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Amiga MA Magazine 1998 #6
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amigamamagazinepolishissue1998.iso
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mesa-1.2.8
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blendxor.c
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C/C++ Source or Header
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1996-05-27
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4KB
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176 lines
/*
** blendxor.c - Demonstrates the use of the blend_logic_op
** extension to draw hilights. Using XOR to draw the same
** image twice restores the background to its original value.
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include "gltk.h"
GLenum doubleBuffer, directRender;
int dithering = 0;
GLint windW, windH;
static void Init(void)
{
glDisable(GL_DITHER);
glShadeModel(GL_FLAT);
}
static void Reshape(int width, int height)
{
windW = (GLint)width;
windH = (GLint)height;
glViewport(0, 0, (GLint)width, (GLint)height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0, 400, 0, 400);
glMatrixMode(GL_MODELVIEW);
}
static GLenum Key(int key, GLenum mask)
{
switch (key) {
case TK_ESCAPE:
tkQuit();
case TK_d:
dithering = !dithering;
break;
default:
return GL_FALSE;
}
return GL_TRUE;
}
static void Draw(void)
{
float xscale, yscale;
GLfloat x, y;
int i;
glDisable(GL_BLEND);
(dithering) ? glEnable(GL_DITHER) : glDisable(GL_DITHER);
glClearColor(0.5, 0.6, 0.1, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
/* Draw background prims */
glColor3f(0.1, 0.1, 1.0);
glBegin(GL_TRIANGLES);
glVertex2i(5, 5);
glVertex2i(130, 50);
glVertex2i(100, 300);
glEnd();
glColor3f(0.5, 0.2, 0.9);
glBegin(GL_TRIANGLES);
glVertex2i(200, 100);
glVertex2i(330, 50);
glVertex2i(340, 400);
glEnd();
glEnable(GL_BLEND);
glBlendEquationEXT(GL_LOGIC_OP);
glLogicOp(GL_XOR);
/* Draw a set of rectangles across the window */
glColor3f(0.9, 0.2, 0.8);
for(i = 0; i < 400; i+=60) {
glBegin(GL_POLYGON);
glVertex2i(i, 100);
glVertex2i(i+50, 100);
glVertex2i(i+50, 200);
glVertex2i(i, 200);
glEnd();
}
glFlush(); /* Added by Brian Paul */
sleep(2);
/* Redraw the rectangles, which should erase them */
for(i = 0; i < 400; i+=60) {
glBegin(GL_POLYGON);
glVertex2i(i, 100);
glVertex2i(i+50, 100);
glVertex2i(i+50, 200);
glVertex2i(i, 200);
glEnd();
}
glFlush();
if (doubleBuffer) {
tkSwapBuffers();
}
}
static GLenum Args(int argc, char **argv)
{
GLint i;
doubleBuffer = GL_FALSE;
directRender = GL_TRUE;
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-sb") == 0) {
doubleBuffer = GL_FALSE;
} else if (strcmp(argv[i], "-db") == 0) {
doubleBuffer = GL_TRUE;
} else if (strcmp(argv[i], "-dr") == 0) {
directRender = GL_TRUE;
} else if (strcmp(argv[i], "-ir") == 0) {
directRender = GL_FALSE;
} else {
printf("%s (Bad option).\n", argv[i]);
return GL_FALSE;
}
}
return GL_TRUE;
}
void main(int argc, char **argv)
{
GLenum type;
char *s;
char *extName = "GL_EXT_blend_logic_op";
if (Args(argc, argv) == GL_FALSE) {
tkQuit();
}
tkInitPosition(0, 0, 400, 400);
type = TK_RGB;
type |= (doubleBuffer) ? TK_DOUBLE : TK_SINGLE;
type |= (directRender) ? TK_DIRECT : TK_INDIRECT;
tkInitDisplayMode(type);
if (tkInitWindow("Blend XOR") == GL_FALSE) {
tkQuit();
}
/* Make sure blend_logic_op extension is there. */
s = (char *) glGetString(GL_EXTENSIONS);
if (!s)
tkQuit();
if (strstr(s,extName) == 0) {
printf("Blend_logic_op extension is not present.\n");
tkQuit();
}
Init();
tkExposeFunc(Reshape);
tkReshapeFunc(Reshape);
tkKeyDownFunc(Key);
tkDisplayFunc(Draw);
tkExec();
}