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