triangle-rasterization-overdraw: Add a triangle rasterisation overdraw test.

Draws a circle using a triangle fan from a random point using stencil
buffer xor,
can also test clipping by drawing a circle which contains the window.

Ensures all pixels are drawn only once thus testing that all triangles
are rasterised correctly.

Based off Brian Paul's suggestion.

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

3 files changed, 319 insertions, 0 deletions

diff --git a/tests/all.tests b/tests/all.tests
index a63ff4a7..11d064a3 100644
--- a/tests/all.tests
+++ b/tests/all.tests
@@ -327,6 +327,7 @@ add_plain_test(general, 'texunits')
 add_plain_test(general, 'timer_query')
 add_plain_test(general, 'triangle-rasterization')
 general['triangle-rasterization-fbo'] = PlainExecTest(['triangle-rasterization', '-auto', '-fbo'])
+add_plain_test(general, 'triangle-rasterization-overdraw')
 add_plain_test(general, 'two-sided-lighting')
 add_plain_test(general, 'two-sided-lighting-separate-specular')
 add_plain_test(general, 'user-clip')
diff --git a/tests/general/CMakeLists.gl.txt b/tests/general/CMakeLists.gl.txt
index 074b9437..2c93b56a 100644
--- a/tests/general/CMakeLists.gl.txt
+++ b/tests/general/CMakeLists.gl.txt
@@ -109,6 +109,7 @@ piglit_add_executable (texgen texgen.c)
 piglit_add_executable (texunits texunits.c)
 piglit_add_executable (timer_query timer_query.c)
 piglit_add_executable (triangle-rasterization triangle-rasterization.cpp)
+piglit_add_executable (triangle-rasterization-overdraw triangle-rasterization-overdraw.cpp)
 piglit_add_executable (two-sided-lighting two-sided-lighting.c)
 piglit_add_executable (two-sided-lighting-separate-specular two-sided-lighting-separate-specular.c)
 piglit_add_executable (user-clip user-clip.c)
diff --git a/tests/general/triangle-rasterization-overdraw.cpp b/tests/general/triangle-rasterization-overdraw.cpp
new file mode 100644
index 00000000..772b3525
--- /dev/null
+++ b/tests/general/triangle-rasterization-overdraw.cpp
@@ -0,0 +1,317 @@
+/**************************************************************************
+ *
+ * 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
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, 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 NON-INFRINGEMENT.
+ * 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
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+/**
+ * Triangle Rasterization Overdraw Test
+ *
+ * Draws a triangle fan to fill the screen and ensures every pixel was drawn only once
+ * Based on idea from Brian Paul
+ *
+ *
+ * Contains two methods of drawing to cover both clipped and unclipped triangles:
+ *
+ *   1. No-Clip: Picks a random point in the window and walks the perimeter of the window
+ *               adding vertices to the triangle fan at non integer steps.
+ *
+ *   2. Clip:    Picks a random point in the window and adds vertices to the triangle fan
+ *               around a circle that contains the entire window, thus going off screen.
+ */
+
+#include "piglit-util.h"
+#include "mersenne.hpp"
+
+#include <time.h>
+#include <vector>
+#include <algorithm>
+
+/* Data structures */
+struct Vector
+{
+   Vector()
+   {
+   }
+
+   Vector(float x, float y)
+      : x(x), y(y)
+   {
+   }
+
+   float x, y;
+};
+
+/* Command line arguments */
+bool rect = false;
+bool clips = false;
+bool break_on_fail = false;
+int random_test_count = 10;
+
+/* Piglit variables */
+int piglit_width = 1000;
+int piglit_height = 1000;
+int piglit_window_mode = GLUT_RGB | GLUT_DOUBLE | GLUT_STENCIL;
+
+/* Globals */
+int test_id = 0;
+Mersenne mersenne;
+
+
+/* Random floating point number between 0 and 1. */
+static inline float
+random_float(void)
+{
+   const int float_range = 1 << 23;
+   return (mersenne.value() % float_range) * (1.0 / float_range);
+}
+
+/* Random float from [a to b) */
+static inline float
+random_float(float a, float b)
+{
+   return a + (b - a - 1) * random_float();
+}
+
+
+struct TestCase
+{
+   Vector mid;
+   std::vector<Vector> triangle_fan;
+
+   struct {
+      int x;
+      int y;
+      int w;
+      int h;
+   } probe_rect;
+
+   void generate(void);
+   bool run(void) const;
+};
+
+
+/* Generates a random triangle fan with a random origin, and contouring a rectangle or circle */
+void TestCase::generate(void)
+{
+   /* Random center point */
+   if (clips) {
+      mid.x = random_float(-0.5*piglit_width, 1.5*piglit_width);
+      mid.y = random_float(-0.5*piglit_height, 1.5*piglit_height);
+   } else {
+      mid.x = random_float(0, piglit_width);
+      mid.y = random_float(0, piglit_height);
+   }
+
+   if (clips) {
+      probe_rect.x = 0;
+      probe_rect.y = 0;
+      probe_rect.w = piglit_width;
+      probe_rect.h = piglit_height;
+   } else {
+      probe_rect.x = piglit_width/4;
+      probe_rect.y = piglit_height/4;
+      probe_rect.w = piglit_width/2;
+      probe_rect.h = piglit_height/2;
+   }
+
+   triangle_fan.clear();
+   triangle_fan.push_back(mid);
+
+   if (rect) {
+      /* Step around the window perimeter adding triangles */
+      double perimeter = probe_rect.w*2 + probe_rect.h*2;
+      double pos = 0.0;
+
+      while (pos < perimeter) {
+         Vector vertex;
+
+         if (pos < probe_rect.w) {
+            /* bottom */
+            vertex.x = probe_rect.x + pos;
+            vertex.y = probe_rect.y + 0.0f;
+         } else if (pos < probe_rect.w + probe_rect.h) {
+            /* right */
+            vertex.x = probe_rect.x + probe_rect.w;
+            vertex.y = probe_rect.y + pos - probe_rect.w;
+         } else if(pos < probe_rect.w*2 + probe_rect.h) {
+            /* top */
+            vertex.x = probe_rect.x + probe_rect.w - (pos - (probe_rect.w + probe_rect.h));
+            vertex.y = probe_rect.y + probe_rect.h;
+         } else {
+            /* left */
+            vertex.x = probe_rect.x + 0.0f;
+            vertex.y = probe_rect.y + probe_rect.h - (pos - (probe_rect.w*2 + probe_rect.h));
+         }
+
+         triangle_fan.push_back(vertex);
+         pos += random_float();
+      }
+   } else {
+      /* Step around a circle that contains the window */
+      double radius = (sqrt(probe_rect.w*probe_rect.w + probe_rect.h*probe_rect.h) / 2.0) + 5.0;
+      double perimeter = 2.0 * M_PI * radius;
+      double pos = 0.0;
+
+      while (pos < perimeter) {
+         double theta = pos / radius;
+
+         float x = probe_rect.x + 0.5 * probe_rect.w + cos(theta) * radius;
+         float y = probe_rect.y + 0.5 * probe_rect.h + sin(theta) * radius;
+
+         triangle_fan.push_back(Vector(x, y));
+         pos += random_float();
+      }
+   }
+
+   /* Complete the fan! */
+   triangle_fan.push_back(triangle_fan.at(1));
+   ++test_id;
+}
+
+/* Tests a triangle fan */
+bool TestCase::run(void) const
+{
+   glViewport(0, 0, piglit_width, piglit_height);
+   piglit_ortho_projection(piglit_width, piglit_height, GL_FALSE);
+
+   /* Set render state */
+   float colour[4];
+   if (rect) {
+      glEnable(GL_BLEND);
+      glBlendEquation(GL_FUNC_ADD);
+      glBlendFunc(GL_ONE, GL_ONE);
+      colour[0] = colour[1] = colour[2] = 127.0f / 255.0f;
+   } else {
+      /* When contouring a circle with very small steps, some overdraw occurs
+       * naturally, but it should cancel itself out, i.e., there should be an
+       * odd number of overdraw inside the shape, and an even number outside.
+       * */
+      glClearStencil(0);
+      glEnable(GL_STENCIL_TEST);
+      glStencilFunc(GL_EQUAL, 0, 1);
+      glStencilOp(GL_INVERT, GL_INVERT, GL_INVERT);
+      colour[0] = colour[1] = colour[2] = 1.0f;
+   }
+
+   colour[3] = 1.0f;
+   glColor4fv(colour);
+
+   glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+   glClear(GL_STENCIL_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
+
+   /* Draw triangle fan */
+   glEnableClientState(GL_VERTEX_ARRAY);
+   glVertexPointer(2, GL_FLOAT, 0, triangle_fan.data());
+   glDrawArrays(GL_TRIANGLE_FAN, 0, triangle_fan.size());
+   glDisableClientState(GL_VERTEX_ARRAY);
+
+   if (!rect) {
+      /* Draw over whole screen, stencil buffer should leave the circle visible */
+      glColor4f(0.0f, 0.0f, 0.0f, 1.0f);
+      piglit_draw_rect(0, 0, piglit_width, piglit_height);
+   }
+
+   /* Reset draw state */
+   glDisable(GL_STENCIL_TEST);
+   glDisable(GL_BLEND);
+
+   if (!piglit_probe_rect_rgb(probe_rect.x, probe_rect.y, probe_rect.w, probe_rect.y, colour)) {
+      printf("%d. Triangle Fan with %d triangles around (%f, %f)\n",
+             test_id, (int)triangle_fan.size(), mid.x, mid.y);
+
+      fflush(stdout);
+      return false;
+   }
+
+   return true;
+}
+
+/* Render */
+enum piglit_result
+piglit_display(void)
+{
+   /* Perform test */
+   GLboolean pass = GL_TRUE;
+
+   TestCase test_case;
+
+   if (piglit_automatic) {
+      int fail_count = 0;
+
+      printf("Running %d random tests\n", random_test_count);
+      fflush(stdout);
+
+      for (int i = 0; i < random_test_count && !(fail_count && break_on_fail); ++i) {
+         test_case.generate();
+         if (!test_case.run())
+            fail_count++;
+      }
+
+      printf("Failed %d random tests\n", fail_count);
+      fflush(stdout);
+
+      if (fail_count)
+         pass = GL_FALSE;
+   } else {
+      test_case.generate();
+      pass &= test_case.run();
+
+      piglit_present_results();
+   }
+
+   assert(glGetError() == 0);
+   return pass ? PIGLIT_PASS : PIGLIT_FAIL;
+}
+
+/* Read command line arguments! */
+void
+piglit_init(int argc, char **argv)
+{
+   uint32_t seed = 0xfacebeef ^ time(NULL);
+
+   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], "-rect") == 0){
+         rect = true;
+      } else if (strcmp(argv[i], "-max_size") == 0){
+         glGetIntegerv(GL_MAX_TEXTURE_SIZE, &piglit_width);
+         piglit_height = piglit_width;
+      } else if (strcmp(argv[i], "-clip") == 0){
+         clips = true;
+         printf("Clipped triangles are being tested\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);
+         }
+      }
+   }
+
+   printf("Random seed: 0x%08X\n", seed);
+   mersenne.init(seed);
+}