msaa: Add files containing the shared code to test multiple draw buffers

Functions defined in these files are utilized by following test cases:
draw-buffers-alpha-to-one
int-draw-buffers-alpha-to-one
draw-buffers-alpha-to-coverage
int-draw-buffers-alpha-to-coverage

V2: Removed unnecessary conditional checks
    Switched to shared visualize_image function
    Updated few comments

Reviewed-by: Paul Berry<stereotype441@gmail.com>

2 files changed, 766 insertions, 0 deletions

diff --git a/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp b/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp
new file mode 100644
index 000000000..7987833d0
--- /dev/null
+++ b/tests/spec/ext_framebuffer_multisample/draw-buffers-common.cpp
@@ -0,0 +1,705 @@
+/*
+ * Copyright © 2012 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "draw-buffers-common.h"
+
+/**
+ * \file draw-buffers-common.cpp
+ *
+ * This file provides utility functions to draw a test pattern to multiple draw
+ * buffers attached to a FBO with GL_SAMPLE_ALPHA_TO_{COVERAGE, ONE}
+ * enabled / disabled.
+ *
+ * Expected color values are computed for each draw buffer based on the enabled
+ * GL_SAMPLE_ALPHA_TO_{COVERAGE, ONE} flags and coverage value used to draw the
+ * test pattern.
+ *
+ * Reference image for each draw buffer is drawn in to right half of default
+ * framebuffer. It is used to verify the accuracy of test image as well as to
+ * visually compare the difference caused by enabling above flags.
+ *
+ * Test image is drawn with the same test pattern in multisample buffer with
+ * GL_SAMPLE_ALPHA_TO_{COVERAGE, ONE} enabled. All multisample draw buffers
+ * are sequentially resolved by  blitting them to a single sample FBO. resolve_fbo
+ * is then blitted to left half of window system framebuffer with appropriate y
+ * offset. This produces three test images in the left half, each corresponds to
+ * a color attachment.
+ *
+ * Test image is verified by comparing it with the corresponding reference
+ * image in the right half
+ *
+ * For sample coverage and sample alpha to coverage, test image should be
+ * verified by probing the rectangles in left half of window system framebuffer
+ * and comparing with expected color values. OpenGL 3.0 specification intends to
+ * allow (but not require) the implementation to produce a dithering effect when
+ * the coverage value is not a strict multiple of 1 / num_samples. We will skip
+ * computing expected values and probing for such rectangles. They are drawn
+ * just to look for dithering by human inspection.
+ *
+ * Note:
+ * At present, the test always uses three draw buffers.  To test other
+ * numbers of draw buffers, we would have to modify the fragment shader in
+ * nontrivial ways at run time.
+ *
+ * Also, the test always uses GL_RGBA8I as integer format or GL_RGBA as float
+ * format for draw buffer zero.
+ *
+ * Author: Anuj Phogat <anuj.phogat@gmail.com>
+ */
+
+static Fbo ms_fbo, resolve_fbo, resolve_int_fbo;
+static GLbitfield buffer_to_test;
+
+static float *coverage = NULL;
+static float *color = NULL;
+static float *expected = NULL;
+
+static int num_draw_buffers;
+static int num_samples;
+static int num_rects;
+static int prog;
+static int color_loc;
+static int frag_0_color_loc;
+static int alpha_to_coverage_loc;
+static int pattern_width;
+static int pattern_height;
+
+static bool is_buffer_zero_integer_format = false;
+
+static const int num_components = 4; /* for RGBA formats */
+static const int num_color_bits = 8; /* for GL_RGBA & GL_RGBA8I formats */
+
+static const float bg_color[4] = {
+	0.0, 0.6, 0.0, 0.4 };
+
+/* Testing for three draw buffers is supported */
+static const GLenum draw_buffers[] = {
+	GL_COLOR_ATTACHMENT0_EXT,
+	GL_COLOR_ATTACHMENT1_EXT,
+	GL_COLOR_ATTACHMENT2_EXT };
+
+static const char *vert =
+	"#version 130\n"
+	"in vec2 pos;\n"
+	"uniform float depth;\n"
+	"void main()\n"
+	"{\n"
+	"  gl_Position = gl_ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0);\n"
+	"}\n";
+
+/* Fragment shader outputs to three draw buffers. Output different alpha values
+ * to different draw buffers. This is required to verify that alpha values from
+ * draw buffer zero are used to determine the fragment coverage value for all
+ * the draw buffers.
+ */
+static const char *frag_template =
+	"#version 130\n"
+	"#define OUT_TYPE %s\n"
+	"out OUT_TYPE frag_out_0;\n"
+	"out vec4 frag_out_1;\n"
+	"out vec4 frag_out_2;\n"
+	"uniform OUT_TYPE frag_0_color;\n"
+	"uniform vec4 color;\n"
+	"uniform bool alphatocoverage;\n"
+	"void main()\n"
+	"{\n"
+	"  frag_out_0 = frag_0_color;\n"
+	"  if(alphatocoverage) {\n"
+	"    frag_out_1 = vec4(color.rgb, color.a / 2);\n"
+	"    frag_out_2 = vec4(color.rgb, color.a / 4);\n"
+	"  }\n"
+	"  else {\n"
+	"    frag_out_1 = frag_out_2 = color;\n"
+	"  }\n"
+	"}\n";
+
+const char *
+get_out_type_glsl(void)
+{
+	if(is_buffer_zero_integer_format)
+		return "ivec4";
+	else
+		return "vec4";
+}
+void
+shader_compile(void)
+{
+	/* Compile program */
+	GLint vs = piglit_compile_shader_text(GL_VERTEX_SHADER, vert);
+
+	const char *out_type_glsl = get_out_type_glsl();;
+        unsigned frag_alloc_len = strlen(frag_template) +
+				  strlen(out_type_glsl) + 1;
+	char *frag = (char *) malloc(frag_alloc_len);
+	sprintf(frag, frag_template, out_type_glsl);
+
+	GLint fs = piglit_compile_shader_text(GL_FRAGMENT_SHADER, frag);
+	prog = piglit_link_simple_program(vs, fs);
+
+	if (!piglit_link_check_status(prog)) {
+		piglit_report_result(PIGLIT_FAIL);
+	}
+	free(frag);
+
+	glBindFragDataLocation(prog, 0, "frag_out_0");
+	/* For multiple draw buffers */
+	if (num_draw_buffers > 1) {
+		glBindFragDataLocation(prog, 1, "frag_out_1");
+		glBindFragDataLocation(prog, 2, "frag_out_2");
+	}
+
+	glBindAttribLocation(prog, 0, "pos");
+	glEnableVertexAttribArray(0);
+
+	/* Linking is rquired after glBindFragDataLocation */
+	piglit_LinkProgram(prog);
+
+	/* Set up uniforms */
+	glUseProgram(prog);
+	color_loc = glGetUniformLocation(prog, "color");
+	frag_0_color_loc = glGetUniformLocation(prog, "frag_0_color");
+	alpha_to_coverage_loc = glGetUniformLocation(prog, "alphatocoverage");
+}
+
+void
+allocate_data_arrays(void)
+{
+	float alpha_scale;
+	/* Draw 2N + 1 rectangles for N samples, each with a unique color
+	 * and coverage value
+	 */
+	if(num_samples) {
+		num_rects = 2 * num_samples + 1;
+		alpha_scale = (1.0 / (2.0 * num_samples));
+	}
+	else {
+		num_rects = 9;
+		alpha_scale = 0.125;
+	}
+
+	/* Allocate data arrays based on number of samples used */
+	color = (float *) malloc(num_rects * num_components * sizeof(float));
+	coverage = (float *) malloc(num_rects * sizeof(float));
+	expected = (float *) malloc(num_draw_buffers * num_rects *
+				    num_components * sizeof(float));
+
+	for(int i = 0; i < num_rects; i++) {
+		unsigned rect_idx = i * num_components;
+		for(int j = 0; j < num_components - 1; j++) {
+			color[rect_idx + j] =
+			(sin((float)(rect_idx + j)) + 1) / 2;
+		}
+		/* Alpha value will be directly used as coverage */
+		if (num_samples)
+			color[rect_idx + 3] = i * alpha_scale;
+		else
+			color[rect_idx + 3] = i * alpha_scale;
+	}
+}
+
+void
+free_data_arrays(void)
+{
+	free(color);
+	color = NULL;
+	free(coverage);
+	coverage = NULL;
+	free(expected);
+	expected = NULL;
+}
+
+void
+float_color_to_int_color(int *dst, float *src)
+{
+	float offset = 1 - pow(2, (num_color_bits - 1));
+	float scale = -2.0 * offset;
+
+	for (int j = 0; j < num_rects; ++j) {
+		for (int k = 0; k < num_components; ++k) {
+			dst[j * num_components + k] =
+			scale * src[j * num_components + k] + offset;
+		}
+	}
+}
+
+void
+draw_pattern(bool sample_alpha_to_coverage,
+	     bool sample_alpha_to_one,
+	     bool is_reference_image,
+	     float *float_color)
+{
+	glUseProgram(prog);
+	glClearColor(bg_color[0], bg_color[1],
+		     bg_color[2], bg_color[3]);
+	glClear(buffer_to_test);
+
+	if(!is_reference_image) {
+		if(sample_alpha_to_coverage)
+			glEnable (GL_SAMPLE_ALPHA_TO_COVERAGE);
+		if(sample_alpha_to_one)
+			glEnable (GL_SAMPLE_ALPHA_TO_ONE);
+	}
+	glUniform1i(alpha_to_coverage_loc, sample_alpha_to_coverage);
+
+	unsigned indices[6] = {0, 1, 2, 0, 2, 3};
+	int integer_color[num_rects * num_components];
+
+	/* For integer color buffers convert the color data to integer format */
+        if(is_buffer_zero_integer_format) {
+		float_color_to_int_color(integer_color, float_color);
+	}
+
+	for (int i = 0; i < num_rects; ++i) {
+		float vertices[4][2] = {
+		{ 0.0f, 0.0f + i * (pattern_height / num_rects) },
+		{ 0.0f, (i + 1.0f) * (pattern_height / num_rects) },
+		{ pattern_width, (i + 1.0f) * (pattern_height / num_rects) },
+		{ pattern_width, 0.0f + i * (pattern_height / num_rects) } };
+
+		glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE,
+				      sizeof(vertices[0]),
+				      (void *) vertices);
+
+		glUniform4fv(color_loc, 1, (float_color + i * num_components));
+		if(is_buffer_zero_integer_format) {
+			glUniform4iv(frag_0_color_loc, 1,
+				     integer_color + i * num_components);
+		}
+		else {
+			glUniform4fv(frag_0_color_loc, 1,
+				     (float_color + i * num_components));
+		}
+		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT,
+			       (void *) indices);
+	}
+	glDisable (GL_SAMPLE_ALPHA_TO_COVERAGE);
+	glDisable (GL_SAMPLE_ALPHA_TO_ONE);
+}
+
+void
+compute_expected(bool sample_alpha_to_coverage,
+		 bool sample_alpha_to_one,
+		 int draw_buffer_count)
+{
+	int i, j;
+	unsigned buffer_idx_offset = draw_buffer_count *
+				     num_rects *
+				     num_components;
+
+	/* Compute the coverage value used in the test */
+	if (num_samples &&
+	    sample_alpha_to_coverage &&
+	    !is_buffer_zero_integer_format) {
+
+		for (i = 0; i < num_rects; i++) {
+			/* Coverage value for all the draw buffers comes from
+			 * the fragment alpha values of draw buffer zero
+			 */
+			float frag_alpha = color[i * num_components + 3];
+			coverage[i] = (frag_alpha < 1.0) ? frag_alpha : 1.0;
+		}
+	}
+	else {
+		for (i = 0; i < num_rects; i++)
+			coverage[i] = 1.0;
+	}
+
+	/* Coverage value decides the number of samples in multisample buffer
+	 * covered by an incoming fragment, which will then receive the
+	 * fragment data. When the multisample buffer is resolved it gets
+	 * blended with the background color which is written to the remaining
+	 * samples.
+	 * Page 254 (page 270 of the PDF) of the OpenGL 3.0 spec says:
+	 * "The method of combination is not specified, though a simple average
+	 * computed independently for each color component is recommended."
+	 * This is followed by NVIDIA and AMD in their proprietary drivers.
+	 */
+	for (i = 0; i < num_rects; i++) {
+
+		float samples_used = coverage[i] * num_samples;
+		/* Expected color values are computed only for integer
+		 * number of samples_used. Non-integer values may result
+		 * in dithering effect.
+		 */
+		if(samples_used == (int) samples_used) {
+			int rect_idx_offset = buffer_idx_offset +
+					      i * num_components;
+			for (j = 0; j < num_components - 1 ; j++) {
+
+				expected[rect_idx_offset + j] =
+				color[i * num_components + j] * coverage[i] +
+				bg_color[j] * (1 - coverage[i]);
+			}
+
+			/* Compute expected alpha values of draw buffers */
+			float frag_alpha = color[i * num_components + 3];
+			int alpha_idx = rect_idx_offset + 3;
+
+			if ((!num_samples &&
+			     !sample_alpha_to_coverage) ||
+			    is_buffer_zero_integer_format) {
+				/* Taking in account alpha values modified by
+				 * fragment shader.
+				 */
+				expected[alpha_idx] =
+					is_buffer_zero_integer_format ?
+					frag_alpha / pow(2, draw_buffer_count) :
+					frag_alpha;
+			}
+			else if (sample_alpha_to_coverage) {
+				/* Taking in account alpha values modified by
+				 * fragment shader.
+				 */
+				frag_alpha /= pow(2, draw_buffer_count);
+				if(sample_alpha_to_one) {
+					expected[alpha_idx] =
+					1.0 * coverage[i] +
+					bg_color[3] * (1 - coverage[i]);
+				}
+				else {
+					expected[alpha_idx] =
+					frag_alpha * coverage[i] +
+					bg_color[3] * (1 - coverage[i]);
+				}
+			}
+			else {
+				expected[alpha_idx] =
+					sample_alpha_to_one ? 1.0 : frag_alpha;
+			}
+		}
+	}
+}
+
+/* This function probes all the draw buffers blitted to downsampled FBO
+ * (resolve_fbo / resolve_int_fbo) and compare against expected color values.
+ */
+bool
+probe_framebuffer_color(void)
+{
+	bool result = true;
+	int * expected_int_color = NULL;
+	int rect_width = pattern_width;
+	int rect_height = pattern_height / num_rects;
+
+	for (int i = 0; i < num_draw_buffers; i++) {
+		bool is_integer_operation = is_buffer_zero_integer_format && !i;
+
+		if(is_integer_operation) {
+			glBindFramebuffer(GL_READ_FRAMEBUFFER,
+					  resolve_int_fbo.handle);
+			expected_int_color = (int*) malloc(num_rects *
+							   num_components *
+							   sizeof(int));
+		}
+		else {
+			glBindFramebuffer(GL_READ_FRAMEBUFFER,
+					  resolve_fbo.handle);
+		}
+
+		for (int j = 0; j < num_rects; j++) {
+			float samples_used = coverage[j] * num_samples;
+			int rect_x = 0;
+			int rect_y = i * pattern_height +
+				     j * (pattern_height / num_rects);
+			int rect_idx_offset = (i * num_rects + j) *
+					      num_components;
+
+			/* Only probe rectangles with coverage value which is a
+			 * strict  multiple of 1 / num_samples.
+			 */
+			if(samples_used == (int)samples_used) {
+				if(is_integer_operation) {
+					float_color_to_int_color(expected_int_color,
+								 expected);
+					result = piglit_probe_rect_rgba_int(
+						 rect_x,
+						 rect_y,
+						 rect_width,
+						 rect_height,
+						 expected_int_color +
+						 rect_idx_offset)
+						 && result;
+				}
+				else {
+					result = piglit_probe_rect_rgba(
+						 rect_x,
+						 rect_y,
+						 rect_width,
+						 rect_height,
+						 expected + rect_idx_offset)
+						 && result;
+				}
+			}
+		}
+	}
+	if(expected_int_color)
+		free(expected_int_color);
+	return result;
+}
+
+void
+draw_image_to_window_system_fb(int draw_buffer_count, bool rhs)
+{
+	unsigned rect_x = 0;
+	unsigned rect_y = draw_buffer_count * pattern_height;
+	unsigned array_size = num_components * pattern_width * pattern_height;
+	float *image = (float *) malloc(sizeof(float) * array_size);
+
+	if(is_buffer_zero_integer_format && draw_buffer_count == 0) {
+		glBindFramebuffer(GL_READ_FRAMEBUFFER, resolve_int_fbo.handle);
+		int *tmp = (int *) malloc(sizeof(int) * array_size);
+		glReadPixels(rect_x, rect_y,
+			     pattern_width, pattern_height,
+			     GL_RGBA_INTEGER,
+			     GL_INT, tmp);
+		for (unsigned i = 0; i < array_size; ++i) {
+			image[i] = tmp[i];
+		}
+
+		/* Convert integer color data to float color data */
+		float color_offset = 1.0 - pow(2.0, num_color_bits - 1);
+		float color_scale = -2.0 * color_offset;
+
+		for (unsigned i = 0; i < array_size; ++i) {
+			image[i] = (image[i] - color_offset) / color_scale;
+		}
+		free(tmp);
+	}
+	else{
+		glBindFramebuffer(GL_READ_FRAMEBUFFER, resolve_fbo.handle);
+		glReadPixels(rect_x, rect_y,
+			     pattern_width,
+			     pattern_height,
+			     GL_RGBA,
+			     GL_FLOAT, image);
+	}
+	visualize_image(image, GL_RGBA,
+			pattern_width, pattern_height,
+			draw_buffer_count + 1, rhs);
+	free(image);
+}
+
+void
+draw_test_image(bool sample_alpha_to_coverage, bool sample_alpha_to_one)
+{
+	/* Draw test pattern in multisample ms_fbo with
+	 * GL_SAMPLE_ALPHA_TO_COVERAGE enabled
+	 */
+	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
+	glDrawBuffers(num_draw_buffers, draw_buffers);
+	ms_fbo.set_viewport();
+
+	draw_pattern(sample_alpha_to_coverage,
+		     sample_alpha_to_one,
+		     false /* is_reference_image */,
+		     color);
+
+	for(int i = 0; i < num_draw_buffers; i++) {
+
+		/* Blit ms_fbo to singlesample FBO to resolve multisample
+		 * buffer.
+		 */
+		glBindFramebuffer(GL_READ_FRAMEBUFFER, ms_fbo.handle);
+		if(buffer_to_test == GL_COLOR_BUFFER_BIT)
+			glReadBuffer(GL_COLOR_ATTACHMENT0_EXT + i);
+
+		if ( is_buffer_zero_integer_format && !i)
+			glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
+					  resolve_int_fbo.handle);
+		else
+			glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
+					  resolve_fbo.handle);
+
+		/* Blit all the draw buffers to resolve_fbo / resolve_int_fbo
+		 * with different y_offset.
+		 */
+		unsigned y_offset = i * pattern_height;
+		glBlitFramebuffer(0, 0,
+				  pattern_width, pattern_height,
+				  0, y_offset,
+				  pattern_width, pattern_height + y_offset,
+				  buffer_to_test, GL_NEAREST);
+
+		draw_image_to_window_system_fb(i /* draw_buffer_count */,
+					       false /* rhs */);
+
+		/* Expected color values for all the draw buffers are computed
+		 * to aid probe_framebuffer_color() in verification.
+		 */
+		if(sample_alpha_to_coverage) {
+			/* Expected color is different for different draw
+			 * buffers
+			 */
+			compute_expected(sample_alpha_to_coverage,
+					 sample_alpha_to_one,
+					 i /* draw_buffer_count */);
+		}
+	}
+}
+
+void
+draw_reference_image(bool sample_alpha_to_coverage, bool sample_alpha_to_one)
+{
+	/* Draw test pattern in multisample ms_fbo with
+	 * GL_SAMPLE_ALPHA_TO_COVERAGE disabled.
+	 */
+	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
+	glDrawBuffers(num_draw_buffers, draw_buffers);
+	ms_fbo.set_viewport();
+
+	if(sample_alpha_to_coverage) {
+		draw_pattern(sample_alpha_to_coverage,
+			     sample_alpha_to_one,
+			     true /* is_reference_image */,
+			     color);
+	}
+	else {
+		/* Value of draw_buffer_count doesn't matter in this case */
+		compute_expected(sample_alpha_to_coverage,
+				 sample_alpha_to_one,
+				 0 /* draw_buffer_count */);
+		draw_pattern(sample_alpha_to_coverage,
+			     sample_alpha_to_one,
+			     true /* is_reference_image */,
+			     expected);
+	}
+
+	for(int i = 0; i < num_draw_buffers; i++) {
+
+		/* Blit ms_fbo to resolve_fbo to resolve multisample buffer */
+		glBindFramebuffer(GL_READ_FRAMEBUFFER, ms_fbo.handle);
+		glReadBuffer(GL_COLOR_ATTACHMENT0_EXT + i);
+		if (is_buffer_zero_integer_format && !i) {
+			glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
+					  resolve_int_fbo.handle);
+		}
+		else {
+			glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
+					  resolve_fbo.handle);
+		}
+
+		/* Blit all the draw buffers to resolve_fbo with different
+		 * y_offset.
+		 */
+		unsigned y_offset = i * pattern_height;
+		glBlitFramebuffer(0, 0,
+				  pattern_width, pattern_height,
+				  0, y_offset,
+				  pattern_width, pattern_height + y_offset,
+				  buffer_to_test, GL_NEAREST);
+
+		draw_image_to_window_system_fb(i /* buffer_count */,
+					       true  /* rhs */ );
+	}
+}
+
+void
+ms_fbo_and_draw_buffers_setup(int samples,
+			      int width,
+			      int height,
+			      int n_attachments,
+			      GLenum test_buffer,
+			      GLenum color_buffer_zero_format)
+{
+	int maxBuffers;
+	glGetIntegerv(GL_MAX_COLOR_ATTACHMENTS, &maxBuffers);
+
+	/* Ensure that requested number of color attachments are
+	 * supported by the implementation and fragment shader.
+	 */
+	if (n_attachments <= (int) ARRAY_SIZE(draw_buffers) &&
+	    n_attachments <= maxBuffers)
+		num_draw_buffers = n_attachments;
+	else {
+		printf("Number of attachments requested are not supported\n");
+		piglit_report_result(PIGLIT_SKIP);
+	}
+
+	pattern_width = width;
+	pattern_height = height;
+
+	/* Setup frame buffer objects with required configuration */
+	FboConfig ms_config(samples, pattern_width, pattern_height);
+	ms_config.color_internalformat = color_buffer_zero_format;
+	ms_fbo.setup(ms_config);
+
+	/* Create resolve_fbo with dimensions large enough to accomodate
+	 * all the draw buffers
+	 */
+	FboConfig resolve_config(0, pattern_width,
+				 num_draw_buffers * pattern_height);
+	resolve_config.color_internalformat = GL_RGBA;
+	resolve_fbo.setup(resolve_config);
+
+	/* Create resolve_int_fbo to store downsampled integer draw buffer */
+	if (color_buffer_zero_format == GL_RGBA8I) {
+		resolve_config.color_internalformat = GL_RGBA8I;
+		/* Assuming single integer buffer */
+		resolve_config.height = pattern_height;
+		resolve_int_fbo.setup(resolve_config);
+		is_buffer_zero_integer_format = true;
+	}
+	else if (color_buffer_zero_format != GL_RGBA){
+		printf("Draw buffer zero format is not"
+		       " supported by test functions.\n");
+		piglit_report_result(PIGLIT_FAIL);
+	}
+
+        if (!piglit_check_gl_error(GL_NO_ERROR)) {
+		printf("Error setting up frame buffer objects\n");
+		piglit_report_result(PIGLIT_FAIL);
+        }
+
+	/* Query the number of samples used in ms_fbo. OpenGL implementation
+	 * may create FBO with more samples per pixel than what is requested.
+	 */
+	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
+	glGetIntegerv(GL_SAMPLES, &num_samples);
+
+	/* Attach additional color buffers to multisample FBO with default
+	 * non-integer format (GL_RGBA.)
+	 */
+	GLuint color_rb[num_draw_buffers - 1];
+	glGenRenderbuffers(num_draw_buffers - 1, color_rb);
+
+	for(int i = 0; i < num_draw_buffers - 1; i++) {
+		glBindRenderbuffer(GL_RENDERBUFFER, color_rb[i]);
+		glRenderbufferStorageMultisample(GL_RENDERBUFFER,
+					ms_fbo.config.num_samples,
+					GL_RGBA,
+					ms_fbo.config.width,
+					ms_fbo.config.height);
+
+		glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER,
+					  GL_COLOR_ATTACHMENT0 + (i + 1),
+					  GL_RENDERBUFFER,
+					  color_rb[i]);
+	}
+
+	GLenum status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
+        if (status != GL_FRAMEBUFFER_COMPLETE) {
+		printf("Error attaching additional color buffers\n");
+		piglit_report_result(PIGLIT_FAIL);
+	}
+	buffer_to_test = test_buffer;
+}
diff --git a/tests/spec/ext_framebuffer_multisample/draw-buffers-common.h b/tests/spec/ext_framebuffer_multisample/draw-buffers-common.h
new file mode 100644
index 000000000..1060eeba8
--- /dev/null
+++ b/tests/spec/ext_framebuffer_multisample/draw-buffers-common.h
@@ -0,0 +1,61 @@
+/* Copyright © 2012 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "common.h"
+
+/**
+ * \file draw-buffers-common.h
+ * This file declares common functions which are used by multiple draw buffer
+ * test cases.
+ */
+
+/* Allocates all the relevant data arrays required in the test */
+void allocate_data_arrays(void);
+
+/* Draws a test pattern without sample_alpha_to_coverage and
+ * sample_alpha_to_one
+ */
+void draw_reference_image(bool sample_alpha_to_coverage,
+			  bool sample_alpha_to_one);
+
+/* Draws the test pattern with either sample_alpha_to_coverage or
+ * sample_alpha_to_one enabled
+ */
+void draw_test_image(bool sample_alpha_to_coverage,
+		     bool sample_alpha_to_one);
+
+/* Frees the previously allocated data arrays */
+void free_data_arrays(void);
+
+/* Initilaizes multisample framebuffer object with multiple draw buffers */
+void ms_fbo_and_draw_buffers_setup(int samples,
+				   int width, int height,
+				   int n_attachments,
+				   GLenum test_buffers,
+				   GLenum color_buffer_zero_format);
+
+/* Probe downsampled FBO (resolve_fbo / resolve_int_fbo) to compare against
+ * expected color for each draw buffer
+ */
+bool probe_framebuffer_color(void);
+
+void shader_compile(void);