path: root/tests/general/triangle-rasterization.cpp

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 *
 * Copyright 2012 VMware, Inc.
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
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 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
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 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS 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
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/**
 * Triangle Rasterization Test
 *
 * This tests OpenGL triangle rasterization by comparing it with a software rasteriser
 *
 * There are 2 components to the test;
 *   1. Predefined sanity tests ensuring bounding box calculations are correct
 *   2. Randomised triangle drawing to attempt to test all possible triangles
 */

#include "piglit-util-gl.h"
#include "mersenne.hpp"

#include <time.h>
#include <vector>
#include <algorithm>

/* Data structures */
struct Vector
{
	Vector()
		: x(0), y(0)
	{
	}

	Vector(float x, float y)
		: x(x), y(y)
	{
	}

	float x, y;
};

struct Triangle {
	Triangle()
	{
	}

	Triangle(const Vector& v0, const Vector& v1, const Vector& v2)
	{
		v[0] = v0;
		v[1] = v1;
		v[2] = v2;
	}

	Vector& operator[](int i)
	{
		return v[i];
	}

	const Vector& operator[](int i) const
	{
		return v[i];
	}

	Vector v[3];
};


/* Command line arguments */
bool use_fbo = false;
bool break_on_fail = false;
bool print_triangle = false;
int random_test_count = 100;

/* filling convention */
static enum filling_convention_t {
	bottom_left = 0,
	left_bottom,
	right_bottom,
	bottom_right,
	top_right,
	right_top,
	left_top,
	top_left,
} filling_convention;

/* Fixed point format */
static int FIXED_SHIFT;
static int FIXED_ONE;

/* Default test size */
int fbo_width = 256;
int fbo_height = 256;

/* Piglit variables */

PIGLIT_GL_TEST_CONFIG_BEGIN

	config.supports_gl_compat_version = 10;

	config.window_width = fbo_width;
	config.window_height = fbo_height;
	config.window_visual = PIGLIT_GL_VISUAL_RGBA | PIGLIT_GL_VISUAL_DOUBLE;

PIGLIT_GL_TEST_CONFIG_END

/* Globals */
int test_id = 0;
Mersenne mersenne;
std::vector<Triangle> fixed_tests;


/* std::algorithm min/max with 3 arguments! :D */
namespace std {
	template<typename T>
	T min(T& a, T& b, T& c)
	{
		return (a < b) ? std::min(a, c) : std::min(b, c);
	}

	template<typename T>
	T max(T& a, T& b, T& c)
	{
		return (a > b) ? std::max(a, c) : std::max(b, c);
	}
}

/* Proper rounding of float to integer */
int64_t iround(float v)
{
	if (v > 0.0f)
		v += 0.5f;
	if (v < 0.0f)
		v -= 0.5f;
	return (int64_t)v;
}

/* Calculate log2 for integers */
int log2i(int x)
{
	int res = 0 ;
	while (x >>= 1)
		++res;
	return res ;
}


/* Based on http://devmaster.net/forums/topic/1145-advanced-rasterization */
void rast_triangle(uint8_t* buffer, uint32_t stride, const Triangle& tri)
{
	float center_offset = -0.5f;

	/* fixed point coordinates */
	int64_t x1 = iround(FIXED_ONE * (tri[0].x + center_offset));
	int64_t x2 = iround(FIXED_ONE * (tri[1].x + center_offset));
	int64_t x3 = iround(FIXED_ONE * (tri[2].x + center_offset));

	int64_t y1 = iround(FIXED_ONE * (tri[0].y + center_offset));
	int64_t y2 = iround(FIXED_ONE * (tri[1].y + center_offset));
	int64_t y3 = iround(FIXED_ONE * (tri[2].y + center_offset));

	/* Force correct vertex order */
	const int64_t cross = (x2 - x1) * (y3 - y2) - (y2 - y1) * (x3 - x2);
	if (cross > 0) {
		std::swap(x1, x3);
		std::swap(y1, y3);
	}

	/* Deltas */
	const int64_t dx12 = x1 - x2;
	const int64_t dx23 = x2 - x3;
	const int64_t dx31 = x3 - x1;

	const int64_t dy12 = y1 - y2;
	const int64_t dy23 = y2 - y3;
	const int64_t dy31 = y3 - y1;

	/* Fixed-point deltas */
	const int64_t fdx12 = dx12 << FIXED_SHIFT;
	const int64_t fdx23 = dx23 << FIXED_SHIFT;
	const int64_t fdx31 = dx31 << FIXED_SHIFT;

	const int64_t fdy12 = dy12 << FIXED_SHIFT;
	const int64_t fdy23 = dy23 << FIXED_SHIFT;
	const int64_t fdy31 = dy31 << FIXED_SHIFT;

	/* Bounding rectangle */
	int64_t minx = std::min(x1, x2, x3) >> FIXED_SHIFT;
	int64_t maxx = (std::max(x1, x2, x3)) >> FIXED_SHIFT;

	int64_t miny = (std::min(y1, y2, y3)) >> FIXED_SHIFT;
	int64_t maxy = std::max(y1, y2, y3) >> FIXED_SHIFT;

	minx = std::max(minx, (int64_t)0);
	maxx = std::min(maxx, (int64_t)fbo_width - 1);

	miny = std::max(miny, (int64_t)0);
	maxy = std::min(maxy, (int64_t)fbo_height - 1);

	/* Half-edge constants */
	int64_t c1 = dy12 * x1 - dx12 * y1;
	int64_t c2 = dy23 * x2 - dx23 * y2;
	int64_t c3 = dy31 * x3 - dx31 * y3;

	/* Correct for filling convention */
	switch (filling_convention) {
		case bottom_right:
			if (dy12 > 0 || (dy12 == 0 && dx12 > 0)) c1++;
			if (dy23 > 0 || (dy23 == 0 && dx23 > 0)) c2++;
			if (dy31 > 0 || (dy31 == 0 && dx31 > 0)) c3++;
			break;
		case right_bottom:
			if (dx12 < 0 || (dx12 == 0 && dy12 < 0)) c1++;
			if (dx23 < 0 || (dx23 == 0 && dy23 < 0)) c2++;
			if (dx31 < 0 || (dx31 == 0 && dy31 < 0)) c3++;
			break;
		case left_bottom:
			if (dx12 < 0 || (dx12 == 0 && dy12 > 0)) c1++;
			if (dx23 < 0 || (dx23 == 0 && dy23 > 0)) c2++;
			if (dx31 < 0 || (dx31 == 0 && dy31 > 0)) c3++;
			break;
		case bottom_left:
			if (dy12 < 0 || (dy12 == 0 && dx12 > 0)) c1++;
			if (dy23 < 0 || (dy23 == 0 && dx23 > 0)) c2++;
			if (dy31 < 0 || (dy31 == 0 && dx31 > 0)) c3++;
			break;
		case top_left:
			if (dy12 < 0 || (dy12 == 0 && dx12 < 0)) c1++;
			if (dy23 < 0 || (dy23 == 0 && dx23 < 0)) c2++;
			if (dy31 < 0 || (dy31 == 0 && dx31 < 0)) c3++;
			break;
		case left_top:
			if (dx12 > 0 || (dx12 == 0 && dy12 > 0)) c1++;
			if (dx23 > 0 || (dx23 == 0 && dy23 > 0)) c2++;
			if (dx31 > 0 || (dx31 == 0 && dy31 > 0)) c3++;
			break;
		case right_top:
			if (dx12 > 0 || (dx12 == 0 && dy12 < 0)) c1++;
			if (dx23 > 0 || (dx23 == 0 && dy23 < 0)) c2++;
			if (dx31 > 0 || (dx31 == 0 && dy31 < 0)) c3++;
			break;
		case top_right:
			if (dy12 > 0 || (dy12 == 0 && dx12 < 0)) c1++;
			if (dy23 > 0 || (dy23 == 0 && dx23 < 0)) c2++;
			if (dy31 > 0 || (dy31 == 0 && dx31 < 0)) c3++;
			break;
	}

	int64_t cy1 = c1 + dx12 * (miny << FIXED_SHIFT) - dy12 * (minx << FIXED_SHIFT);
	int64_t cy2 = c2 + dx23 * (miny << FIXED_SHIFT) - dy23 * (minx << FIXED_SHIFT);
	int64_t cy3 = c3 + dx31 * (miny << FIXED_SHIFT) - dy31 * (minx << FIXED_SHIFT);

	/* Perform rasterization */
	buffer += miny * stride;
	for (int64_t y = miny; y <= maxy; y++) {
		int64_t cx1 = cy1;
		int64_t cx2 = cy2;
		int64_t cx3 = cy3;

		for (int64_t x = minx; x <= maxx; x++) {
			if (cx1 > 0 && cx2 > 0 && cx3 > 0) {
				((uint32_t*)buffer)[x] = 0x00FF00FF;
			}

			cx1 -= fdy12;
			cx2 -= fdy23;
			cx3 -= fdy31;
		}

		cy1 += fdx12;
		cy2 += fdx23;
		cy3 += fdx31;

		buffer += stride;
	}
}


/* Prints an ascii representation of the triangle */
void triangle_art(uint32_t* buffer)
{
	int minx = fbo_width - 1, miny = fbo_height - 1;
	int maxx = 0, maxy = 0;

	/* Find bounds so we dont have to print whole screen */
	for (int y = 0; y < fbo_height; ++y) {
		for (int x = 0; x < fbo_width; ++x) {
			if (buffer[y*fbo_width + x] & 0xFFFFFF00) {
				if (x < minx) minx = x;
				if (y < miny) miny = y;
				if (x > maxx) maxx = x;
				if (y > maxy) maxy = y;
			}
		}
	}

	/* Nothing drawn */
	if (minx > maxx || miny > maxy)
		return;

	--minx; --miny;
	++maxx; ++maxy;

	/* Print an ascii representation of triangle */
	for (int y = maxy; y >= miny; --y) {
		for (int x = minx; x <= maxx; ++x) {
			uint32_t val = buffer[y*fbo_width + x] & 0xFFFFFF00;

			if (val == 0xFF000000) {
				printf("+");
			} else if (val == 0x00FF0000) {
				printf("-");
			} else if (val == 0xFFFF0000) {
				printf("o");
			} else if (val == 0) {
				printf(".");
			} else {
				printf("?");
			}
		}

		printf("\n");
	}

	printf("\n");
}


/* Reads buffer from OpenGL and checks for any colour other than black or yellow
 * (black = background, yellow = both opengl AND software rast drew to that pixel)
 */
uint32_t* check_triangle()
{
	static uint32_t* buffer = 0;
	if (!buffer) buffer = new uint32_t[fbo_width * fbo_height];

	glReadPixels(0, 0, fbo_width, fbo_height, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, buffer);

	for (int y = 0; y < fbo_height; ++y) {
		for (int x = 0; x < fbo_width; ++x) {
			uint32_t val = buffer[y*fbo_width + x] & 0xFFFFFF00;

			if (val != 0 && val != 0xFFFF0000) {
				return buffer;
			}
		}
	}

	return NULL;
}


/* Performs test using tri */
GLboolean test_triangle(const Triangle& tri)
{
	static uint32_t* buffer = 0;
	if (!buffer) buffer = new uint32_t[fbo_width * fbo_height];

	/* Clear OpenGL and software buffer */
	glClear(GL_COLOR_BUFFER_BIT);
	memset(buffer, 0, sizeof(uint32_t) * fbo_width * fbo_height);

	/* Software rasterise triangle and blit it to OpenGL */
	rast_triangle((uint8_t*)buffer, fbo_width * 4, tri);
	glDrawPixels(fbo_width, fbo_height, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, buffer);

	/* Draw OpenGL triangle */
	glEnableClientState(GL_VERTEX_ARRAY);
	glVertexPointer(2, GL_FLOAT, 0, tri.v);
	glDrawArrays(GL_TRIANGLES, 0, 3);
	glDisableClientState(GL_VERTEX_ARRAY);

	/* Check the result and print relevant error messages */
	if (uint32_t* result = check_triangle()) {
		printf("FAIL: %d. (%f, %f), (%f, %f), (%f, %f)\n", test_id,
		       tri[0].x, tri[0].y, tri[1].x, tri[1].y, tri[2].x, tri[2].y);

		if (print_triangle) {
			triangle_art(result);
		}

		fflush(stdout);
		return GL_FALSE;
	}

	return GL_TRUE;
}


/* Generate a random triangle */
void random_triangle(Triangle& tri)
{
	int size = 1 << (mersenne.value() % (log2i(fbo_width) + 1));

	for (int i = 0; i < 3; ++i) {
		tri[i].x = (mersenne.value() % (size * FIXED_ONE)) * (1.0f / FIXED_ONE);
		tri[i].y = (mersenne.value() % (size * FIXED_ONE)) * (1.0f / FIXED_ONE);
	}

	test_id++;
}


/* From the OpenGL 1.4 spec page 78 (page 91 of PDF):
 * "Special treatment is given to a fragment whose center lies on a polygon
 * boundary edge. In such a case we require that if two polygons lie on either
 * side of a common edge (with identical endpoints) on which a fragment center
 * lies, then exactly one of the polygons results in the production of the
 * fragment during rasterization."
 * Additionally rasterization is required to be invariant under translation
 * along either axis by a multiple of the pixel size (page 63/76).
 *
 * We assume that the implementation adheres to a more stringent convention in
 * which either top, left, bottom or right edges of a triangles 'belong' to it,
 * that is, if one of those edges intersects with a fragment center, the
 * fragment is produced. Additionally, for 'top' and 'bottom'-type triangles
 * either left or right vertical edges 'belong' to it. Similarily the same is
 * true with horizontal edges and 'left' and 'right'-type triangles.
 *
 * For example: consider these 8 triangles centered around a fragment center:
 *   _____
 *  |\2|1/|
 *  |3\|/0|
 *  |-- --|
 *  |4/|\7|
 *  |/5|6\|
 *
 * The rasterizer should produce exactly one fragment. If triangle no. 0
 * produces the fragment, the rasterizer is said to follow the bottom-left
 * convention (bottom because bottom horizontal edges 'belong' to the triangle
 * and left because all left facing edges 'belong' to it).
 *
 * This function determines the convention by drawing the 8 triangles shown
 * above in sub-pixel-size into 8 seperate pixels and checks which
 * pixel is filled.
 */
void get_filling_convention(void)
{
	Triangle tests[8];

	const float mid = 0.5f;
	const float size  = 3.0f / FIXED_ONE;

	const Vector v[] = {
		Vector(mid + size, mid),
		Vector(mid + size, mid + size),
		Vector(mid, mid + size),
		Vector(mid - size, mid + size),
		Vector(mid - size, mid),
		Vector(mid - size, mid - size),
		Vector(mid, mid - size),
		Vector(mid + size, mid - size),
		Vector(mid + size, mid),
	};
	const Vector vm(mid, mid);

	for (int i = 0; i < 8; ++i) {
		tests[i][0] = v[i];
		tests[i][1] = v[i+1];
		tests[i][2] = vm;
	}

	glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	glClear(GL_COLOR_BUFFER_BIT);
	glEnableClientState(GL_VERTEX_ARRAY);
	piglit_ortho_projection(1, 1, GL_FALSE);

	assert(piglit_width >= 8);
	for (int i = 0; i < 8; ++i) {
		glViewport(i, 0, 1, 1);

		/* Draw OpenGL triangle */
		glVertexPointer(2, GL_FLOAT, 0, tests[i].v);
		glDrawArrays(GL_TRIANGLES, 0, 3);
	}

	glDisableClientState(GL_VERTEX_ARRAY);
	glViewport(0, 0, fbo_width, fbo_height);
	piglit_ortho_projection(fbo_width, fbo_height, GL_FALSE);

	uint32_t buffer[8];
	glReadPixels(0, 0, 8, 1, GL_RGBA, GL_UNSIGNED_INT_8_8_8_8, buffer);

	int produced_fragment_count = 0;
	for (int i = 0; i < 8; ++i) {
		if ((buffer[i] & 0xFFFFFF00) == 0xFFFFFF00) {
			filling_convention = (filling_convention_t)i;
			produced_fragment_count++;
		}
	}

	if (produced_fragment_count != 1) {
		printf("Unable to determine filling convention.\n");
		piglit_report_result(PIGLIT_SKIP);
	}
}


/* Render */
enum piglit_result
piglit_display(void)
{
	GLuint fb, tex;

	/* If using FBO, set it up */
	if (use_fbo) {
		glDisable(GL_CULL_FACE);

		glGenTextures(1, &tex);
		glBindTexture(GL_TEXTURE_2D, tex);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
		glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, fbo_width, fbo_height, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);

		glGenFramebuffersEXT(1, &fb);
		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fb);
		glViewport(0, 0, fbo_width, fbo_height);

		glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,
					  GL_COLOR_ATTACHMENT0_EXT,
					  GL_TEXTURE_2D,
					  tex,
					  0);

		if (!piglit_check_gl_error(GL_NO_ERROR))
		        piglit_report_result(PIGLIT_FAIL);
		assert(glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT) == GL_FRAMEBUFFER_COMPLETE_EXT);

		glBindTexture(GL_TEXTURE_2D, 0);
	}

	get_filling_convention();

	/* Set render state */
	glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

	glEnable(GL_BLEND);
	glBlendEquation(GL_FUNC_ADD);
	glBlendFunc(GL_ONE, GL_ONE);

	glViewport(0, 0, fbo_width, fbo_height);
	piglit_ortho_projection(fbo_width, fbo_height, GL_FALSE);

	/* Perform test */
	GLboolean pass = GL_TRUE;
	if (piglit_automatic) {
		int fail_count = 0;

		printf("Running %d fixed tests\n", (int)fixed_tests.size());
		for (std::vector<Triangle>::iterator itr = fixed_tests.begin(); itr != fixed_tests.end() && !(fail_count && break_on_fail); ++itr) {
			if (!test_triangle(*itr))
				++fail_count;
		}

		printf("Running %d random tests\n", random_test_count);
		for (int i = 0; i < random_test_count && !(fail_count && break_on_fail); ++i) {
			Triangle tri;
			random_triangle(tri);

			if (!test_triangle(tri))
				++fail_count;
		}

		printf("Failed %d tests\n", fail_count);
		fflush(stdout);

		if (fail_count)
			pass = GL_FALSE;
	} else {
		Triangle tri;
		random_triangle(tri);
		pass &= test_triangle(tri);

		glDisable(GL_BLEND);

		/* If using FBO, draw the fbo to screen */
		if (use_fbo) {
			glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, piglit_winsys_fbo);
			glViewport(0, 0, piglit_width, piglit_height);
			piglit_ortho_projection(piglit_width, piglit_height, GL_FALSE);

			glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE);
			glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_REPLACE);
			glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA, GL_REPLACE);

			glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
			glEnable(GL_TEXTURE_2D);
			glBindTexture(GL_TEXTURE_2D, tex);

			piglit_draw_rect_tex(0, 0, piglit_width, piglit_height, 0, 0, 1, 1);

			glDisable(GL_TEXTURE_2D);
		}

		piglit_present_results();
	}

	/* Cleanup FBO if necessary */
	if (use_fbo) {
		glDeleteTextures(1, &tex);
		glDeleteFramebuffersEXT(1, &fb);
		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, piglit_winsys_fbo);
	}

	if (!piglit_check_gl_error(GL_NO_ERROR))
		piglit_report_result(PIGLIT_FAIL);

	return pass ? PIGLIT_PASS : PIGLIT_FAIL;
}


/* Create some fixed tests to test bounding box in/exclusivity,
 *
 *  /|\
 * /_|_\  Tests these 4 triangles but shifting them from -1/16 to +1/16
 * \ | /  around the center point
 *  \|/
 */
void init_fixed_tests()
{
	const float mid = 0.5f;
	const float shift = 1.0f / FIXED_ONE;
	const float size  = 3.0f / FIXED_ONE;

	Vector vv[] = {
		Vector(mid, mid + size),
		Vector(mid, mid - size),
	};

	Vector vh[] = {
		Vector(mid - size, mid),
		Vector(mid + size, mid),
	};

	Vector vm(mid, mid);

	/* Loop through the 4 possible triangles */
	for (int vy = 0; vy < 2; ++vy) {
		for (int vx = 0; vx < 2; ++vx) {
			Triangle tri;

			tri[0] = vh[vx];
			tri[1] = vv[vy];
			tri[2] = vm;

			/* Loop through the x and y shifts */
			for (int y = -1; y <= 1; ++y) {
				for (int x = -1; x <= 1; ++x) {
					Triangle shifted = tri;

					for (int i = 0; i < 3; ++i) {
						shifted[i].x += x * shift;
						shifted[i].y += y * shift;
					}

					fixed_tests.push_back(shifted);
				}
			}
		}
	}
}


/* Read command line arguments! */
void
piglit_init(int argc, char **argv)
{
	uint32_t seed = 0xfacebeef ^ time(NULL);
	GLint gl_subpixel_bits, in_subpixel_bits;
	glGetIntegerv(GL_SUBPIXEL_BITS, &gl_subpixel_bits);
	in_subpixel_bits = gl_subpixel_bits;

	for (int i = 1; i < argc; ++i) {
		if (strcmp(argv[i], "-break_on_fail") == 0){
			break_on_fail = true;
			printf("Execution will stop on first fail\n");
		} else if (strcmp(argv[i], "-print_triangle") == 0){
			print_triangle = true;
		} else if (strcmp(argv[i], "-max_size") == 0){
			glGetIntegerv(GL_MAX_TEXTURE_SIZE, &fbo_width);

			fbo_height = fbo_width;
			piglit_width = fbo_width;
			piglit_height = fbo_height;
		} else if (strcmp(argv[i], "-use_fbo") == 0){
			use_fbo = true;
			printf("FBOs are in use\n");
		} else if (i + 1 < argc) {
			if (strcmp(argv[i], "-count") == 0) {
				random_test_count = strtoul(argv[++i], NULL, 0);
			} else if (strcmp(argv[i], "-seed") == 0) {
				seed = strtoul(argv[++i], NULL, 0);
			} else if (strcmp(argv[i], "-subpixel_bits") == 0) {
				in_subpixel_bits = strtoul(argv[++i], NULL, 0);
			}
		}
	}

	FIXED_SHIFT = in_subpixel_bits;
	FIXED_ONE = 1 << FIXED_SHIFT;

	printf("GL indicates %d subpixel bits, using %d subpixel bits\n",
		gl_subpixel_bits, in_subpixel_bits);
	printf("Random seed: 0x%08X\n", seed);
	mersenne.init(seed);

	init_fixed_tests();
}