merge of blend_test and lerabot_blend_test, addition of 1 case, and...

CMakeLists.txt

@@ -124,7 +124,6 @@ gen_sample(depth_funcs samples/depth_funcs/main.c)
 gen_sample(depth_funcs_alpha_testing samples/depth_funcs_alpha_testing/main.c samples/depth_funcs_alpha_testing/gl_png.c)
 gen_sample(depth_funcs_ortho samples/depth_funcs_ortho/main.c)
 gen_sample(lerabot01 samples/lerabot01/main.c)
-gen_sample(lerabot_blend_test samples/lerabot_blend_test/main.c)
 gen_sample(lights samples/lights/main.c)
 gen_sample(mipmap samples/mipmap/main.c)
 gen_sample(multitexture_arrays samples/multitexture_arrays/main.c samples/multitexture_arrays/pvr-texture.c)

samples/blend_test/main.c

@@ -1,7 +1,8 @@
 /*
- * This sample is to demonstrate a bug where rendering an unblended
+ * This sample demonstrates blending, and the importance of drawing order,
- * polygon, before a series of blended ones would result in no blended
+ * depth testing and z-value.
- * output and incorrect depth testing
+ * This is a merge of lerabot_blend_test and blend_test, with 1 added case,
+ * and with adapted/corrected explanation
  */
 
 #ifdef __DREAMCAST__
@@ -82,13 +83,13 @@ void DrawGLScene()
     const float NONE [] = {0, 0, 0, 0};
 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);		// Clear The Screen And The Depth Buffer
+
+    // LEFT UPPER SECTION
     glLoadIdentity();				// Reset The View
-
+    glTranslatef(-4.0, 2.0, -10);
-    glTranslatef(-4.0, 0, -10);
+    // This draws 2 quads, a red first, then an overlapping blue one.
-
+    // Both quads are drawn at the SAME z-value
-    // LEFT SECTION
+    // With depth test GL_LEQUAL, this means blending for the overlapping part
-    // This should draw 2 quad, a red first, then and overlapping blue one.
-    // This section draw both quad at the same Z value
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     DrawQuad(RED);
@@ -96,11 +97,24 @@ void DrawGLScene()
     DrawQuad(BLUE);
     glDisable(GL_BLEND);
 
+    // RIGHT UPPER SECTION
     glTranslatef(4.0, 0, 0);
+    // This draws 2 quads, a red first, then an overlapping blue one.
+    // The blue quad has a LOWER z-value, so it is behind the red quad.
+    // With depth test GL_LEQUAL, the blue part is not considered for the overlapping part, so no blending
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    DrawQuad(RED);
+    glTranslatef(1.0, 0, -0.01);
+    DrawQuad(BLUE);
+    glDisable(GL_BLEND);
 
-    // RIGHT SECTION
+    // LEFT DOWN SECTION
-    // This should draw 2 quad, a red first, then and overlapping blue one.
+    glLoadIdentity();				// Reset The View
-    // This section uses a HIGHER Z VALUE(0.01f), so the blue quad should be in FRONT of the red quad.
+    glTranslatef(-4.0, -1.0, -10);
+    // This draws 2 quads, a red first, then an overlapping blue one.
+    // The blue quad has a HIGHER z-value, so it is in front the red quad.
+    // With depth test GL_LEQUAL, this means blending for the overlapping part
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     DrawQuad(RED);
@@ -108,6 +122,20 @@ void DrawGLScene()
     DrawQuad(BLUE);
     glDisable(GL_BLEND);
 
+    // RIGHT DOWN SECTION
+    glTranslatef(4.0, 0.0, -0.01);
+    // This is basically the same as the RIGHT UPPER SECTION, except that the blue quad
+    //  is drawn first.
+    // With depth test GL_LEQUAL, this means blending for the overlapping part 
+    // <- the order of drawing is important for blending !
+    glEnable(GL_BLEND);
+    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+    glTranslatef(1.0, 0.0, -0.01);
+    DrawQuad(BLUE);
+    glTranslatef(-1.0, 0.0, 0.01);
+    DrawQuad(RED);
+    glDisable(GL_BLEND);
+
     glKosSwapBuffers();
 }
 

samples/lerabot_blend_test/main.c

@@ -1,130 +0,0 @@
-/*
- * This sample is to demonstrate a bug where rendering an unblended
- * polygon, before a series of blended ones would result in no blended
- * output and incorrect depth testing
- */
-
-#ifdef __DREAMCAST__
-#include <kos.h>
-#endif
-
-#include "GL/gl.h"
-#include "GL/glu.h"
-#include "GL/glkos.h"
-
-/* A general OpenGL initialization function.  Sets all of the initial parameters. */
-void InitGL(int Width, int Height)	        // We call this right after our OpenGL window is created.
-{
-    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);		// This Will Clear The Background Color To Black
-    glClearDepth(1.0);				// Enables Clearing Of The Depth Buffer
-    glDepthFunc(GL_LEQUAL);				// The Type Of Depth Test To Do
-    glEnable(GL_DEPTH_TEST);			// Enables Depth Testing
-    glEnable(GL_TEXTURE_2D);
-    glShadeModel(GL_SMOOTH);			// Enables Smooth Color Shading
-    glDisable(GL_BLEND);
-
-    glMatrixMode(GL_PROJECTION);
-    glLoadIdentity();				// Reset The Projection Matrix
-
-    gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);	// Calculate The Aspect Ratio Of The Window
-
-    glMatrixMode(GL_MODELVIEW);
-}
-
-/* The function called when our window is resized (which shouldn't happen, because we're fullscreen) */
-void ReSizeGLScene(int Width, int Height)
-{
-    if (Height == 0)				// Prevent A Divide By Zero If The Window Is Too Small
-        Height = 1;
-
-    glViewport(0, 0, Width, Height);		// Reset The Current Viewport And Perspective Transformation
-
-    glMatrixMode(GL_PROJECTION);
-    glLoadIdentity();
-
-    gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);
-    glMatrixMode(GL_MODELVIEW);
-}
-
-int check_start() {
-#ifdef __DREAMCAST__
-    maple_device_t *cont;
-    cont_state_t *state;
-
-    cont = maple_enum_type(0, MAPLE_FUNC_CONTROLLER);
-
-    if(cont) {
-        state = (cont_state_t *)maple_dev_status(cont);
-
-        if(state)
-            return state->buttons & CONT_START;
-    }
-#endif
-
-    return 0;
-}
-
-void DrawQuad(const float* colour) {
-    glBegin(GL_QUADS);
-    glColor4fv(colour);
-    glVertex3f(-1.0,-1.0, 0.0);
-    glVertex3f( 1.0,-1.0, 0.0);
-    glVertex3f( 1.0, 1.0, 0.0);
-    glVertex3f(-1.0, 1.0, 0.0);
-    glEnd();
-}
-
-/* The main drawing function. */
-void DrawGLScene()
-{
-    const float RED [] = {1.0, 0, 0, 0.5};
-    const float BLUE [] = {0.0, 0, 1, 0.5};
-    const float NONE [] = {0, 0, 0, 0};
-
-    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);		// Clear The Screen And The Depth Buffer
-    glLoadIdentity();				// Reset The View
-
-    glTranslatef(-4.0, 0, -10);
-
-    // LEFT SECTION
-    // This should draw 2 quad, a red first, then and overlapping blue one.
-    // This section draw both quad at the same Z value
-    glEnable(GL_BLEND);
-    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-    DrawQuad(RED);
-    glTranslatef(1.0, 0, 0);
-    DrawQuad(BLUE);
-    glDisable(GL_BLEND);
-
-    glTranslatef(4.0, 0, 0);
-
-    // RIGHT SECTION
-    // This should draw 2 quad, a red first, then and overlapping blue one.
-    // This section uses a LOWER Z VALUE(-0.01f), so the blue quad should be in FRONT of the red quad.
-    // lerabot's note : changing the z value to positive gives the desired output.
-    glEnable(GL_BLEND);
-    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-    DrawQuad(RED);
-    glTranslatef(1.0, 0, -0.01);
-    DrawQuad(BLUE);
-    glDisable(GL_BLEND);
-
-    glKosSwapBuffers();
-}
-
-int main(int argc, char **argv)
-{
-    glKosInit();
-
-    InitGL(640, 480);
-    ReSizeGLScene(640, 480);
-
-    while(1) {
-        if(check_start())
-            break;
-
-        DrawGLScene();
-    }
-
-    return 0;
-}