added a new depth/alpha testing sample

This commit is contained in:
lerabot 2020-05-13 10:34:18 -04:00
parent bd59922052
commit 4e47b30b0a
3 changed files with 135 additions and 0 deletions

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TARGET = blend_test.elf
OBJS = main.o
all: rm-elf $(TARGET)
include $(KOS_BASE)/Makefile.rules
clean:
-rm -f $(TARGET) $(OBJS) romdisk.*
rm-elf:
-rm -f $(TARGET) romdisk.*
$(TARGET): $(OBJS) romdisk.o
$(KOS_CC) $(KOS_CFLAGS) $(KOS_LDFLAGS) -o $(TARGET) $(KOS_START) \
$(OBJS) romdisk.o $(OBJEXTRA) -lm -lkosutils $(KOS_LIBS)
romdisk.img:
$(KOS_GENROMFS) -f romdisk.img -d romdisk -v
romdisk.o: romdisk.img
$(KOS_BASE)/utils/bin2o/bin2o romdisk.img romdisk romdisk.o
run: $(TARGET)
$(KOS_LOADER) $(TARGET)
dist:
rm -f $(OBJS) romdisk.o romdisk.img
$(KOS_STRIP) $(TARGET)

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/*
* 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
*/
#include "gl.h"
#include "glu.h"
#include "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);
}
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) {
DrawGLScene();
}
return 0;
}