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-rw-r--r--progs/glsl/points.c305
1 files changed, 305 insertions, 0 deletions
diff --git a/progs/glsl/points.c b/progs/glsl/points.c
new file mode 100644
index 0000000000..85115de504
--- /dev/null
+++ b/progs/glsl/points.c
@@ -0,0 +1,305 @@
+/**
+ * Implement smooth (AA) points with shaders.
+ * A simple variation could be used for sprite points.
+ * Brian Paul
+ * 29 July 2007
+ */
+
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+#include <GL/gl.h>
+#include <GL/glut.h>
+#include <GL/glext.h>
+#include "extfuncs.h"
+
+
+static GLuint FragShader;
+static GLuint VertShader;
+static GLuint Program;
+
+static GLint Win = 0;
+static GLint WinWidth = 500, WinHeight = 200;
+static GLfloat Xpos = 0.0f, Ypos = 0.0f;
+static GLint uViewportInv;
+static GLboolean Smooth = GL_TRUE, Blend = GL_TRUE;
+
+
+/**
+ * Issue vertices for a "shader point".
+ * The position is duplicated, only texcoords (or other vertex attrib) change.
+ * The vertex program will compute the "real" quad corners.
+ */
+static void
+PointVertex3f(GLfloat x, GLfloat y, GLfloat z)
+{
+ glTexCoord2f(-1, -1);
+ glVertex3f(x, y, z);
+
+ glTexCoord2f( 1, -1);
+ glVertex3f(x, y, z);
+
+ glTexCoord2f( 1, 1);
+ glVertex3f(x, y, z);
+
+ glTexCoord2f(-1, 1);
+ glVertex3f(x, y, z);
+}
+
+
+static void
+DrawPoints(GLboolean shaderPoints)
+{
+ int i;
+ for (i = 0; i < 9; i++) {
+ GLfloat x = i - 4, y = 0, z = 0;
+ /* note: can't call glPointSize inside Begin/End :( */
+ glPointSize( 2 + i * 5 );
+ if (shaderPoints) {
+ glBegin(GL_QUADS);
+ PointVertex3f(x, y, z);
+ glEnd();
+ }
+ else {
+ glBegin(GL_POINTS);
+ glVertex3f(x, y, z);
+ glEnd();
+ }
+ }
+}
+
+
+/**
+ * Top row of points rendered convetionally,
+ * bottom row rendered with shaders.
+ */
+static void
+Redisplay(void)
+{
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+ if (Smooth)
+ glEnable(GL_POINT_SMOOTH);
+ else
+ glDisable(GL_POINT_SMOOTH);
+
+ if (Blend)
+ glEnable(GL_BLEND);
+ else
+ glDisable(GL_BLEND);
+
+ glPushMatrix();
+ glTranslatef(Xpos, Ypos, 0);
+
+ /*
+ * regular points
+ */
+ glPushMatrix();
+ glTranslatef(0, 1.2, 0);
+ glUseProgram_func(0);
+ DrawPoints(GL_FALSE);
+ glPopMatrix();
+
+ /*
+ * shader points
+ */
+ glPushMatrix();
+ glTranslatef(0, -1.2, 0);
+ glUseProgram_func(Program);
+ if (uViewportInv != -1) {
+ glUniform2f_func(uViewportInv, 1.0 / WinWidth, 1.0 / WinHeight);
+ }
+ DrawPoints(GL_TRUE);
+ glPopMatrix();
+
+ glPopMatrix();
+
+ glutSwapBuffers();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+ WinWidth = width;
+ WinHeight = height;
+ glViewport(0, 0, width, height);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ glFrustum(-1.0, 1.0, -1.0, 1.0, 4.0, 30.0);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+ glTranslatef(0.0f, 0.0f, -20.0f);
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+ (void) x;
+ (void) y;
+
+ switch(key) {
+ case 'b':
+ Blend = !Blend;
+ break;
+ case 's':
+ Smooth = !Smooth;
+ break;
+ case 27:
+ glDeleteShader_func(FragShader);
+ glDeleteShader_func(VertShader);
+ glDeleteProgram_func(Program);
+ glutDestroyWindow(Win);
+ exit(0);
+ }
+ glutPostRedisplay();
+}
+
+
+static void
+SpecialKey(int key, int x, int y)
+{
+ const GLfloat step = 1/100.0;
+ switch(key) {
+ case GLUT_KEY_UP:
+ Ypos += step;
+ break;
+ case GLUT_KEY_DOWN:
+ Ypos -= step;
+ break;
+ case GLUT_KEY_LEFT:
+ Xpos -= step;
+ break;
+ case GLUT_KEY_RIGHT:
+ Xpos += step;
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void
+LoadAndCompileShader(GLuint shader, const char *text)
+{
+ GLint stat;
+
+ glShaderSource_func(shader, 1, (const GLchar **) &text, NULL);
+
+ glCompileShader_func(shader);
+
+ glGetShaderiv_func(shader, GL_COMPILE_STATUS, &stat);
+ if (!stat) {
+ GLchar log[1000];
+ GLsizei len;
+ glGetShaderInfoLog_func(shader, 1000, &len, log);
+ fprintf(stderr, "fslight: problem compiling shader:\n%s\n", log);
+ exit(1);
+ }
+}
+
+
+static void
+CheckLink(GLuint prog)
+{
+ GLint stat;
+ glGetProgramiv_func(prog, GL_LINK_STATUS, &stat);
+ if (!stat) {
+ GLchar log[1000];
+ GLsizei len;
+ glGetProgramInfoLog_func(prog, 1000, &len, log);
+ fprintf(stderr, "Linker error:\n%s\n", log);
+ }
+}
+
+
+static void
+Init(void)
+{
+ /* Fragment shader: compute distance of fragment from center of point
+ * (we're using texcoords but another varying could be used).
+ * if dist > 1, discard (coverage==0)
+ * if dist < k, coverage = 1
+ * else, coverage = func(dist)
+ * Note: length() uses sqrt() and may be expensive. The distance could
+ * be squared instead (with adjustments to the threshold (k) test)
+ */
+ static const char *fragShaderText =
+ "void main() {\n"
+ " float cover; \n"
+ " float k = 2.0 / gl_Point.size; \n"
+ " float d = length(gl_TexCoord[0].xy); \n"
+ " if (d >= 1.0) \n"
+ " discard; \n"
+ " if (d < 1.0 - k) \n"
+ " cover = 1.0; \n"
+ " else \n"
+ " cover = (1.0 - d) * 0.5 * gl_Point.size; \n"
+ " gl_FragColor.rgb = gl_Color.rgb; \n"
+ " gl_FragColor.a = cover; \n"
+ "}\n";
+ /* Vertex shader: compute new vertex position based on incoming vertex pos,
+ * texcoords, point size, and inverse viewport scale factor.
+ * Note: should compute point size attenuation here too.
+ */
+ static const char *vertShaderText =
+ "uniform vec2 viewportInv; \n"
+ "void main() {\n"
+ " vec4 pos = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
+ " gl_Position.xy = pos.xy + gl_MultiTexCoord0.xy * viewportInv \n"
+ " * gl_Point.size * pos.w; \n"
+ " gl_Position.zw = pos.zw; \n"
+ " gl_TexCoord[0] = gl_MultiTexCoord0; \n"
+ " gl_FrontColor = gl_Color; \n"
+ "}\n";
+ const char *version;
+
+ version = (const char *) glGetString(GL_VERSION);
+ if (version[0] != '2' || version[1] != '.') {
+ printf("This program requires OpenGL 2.x, found %s\n", version);
+ exit(1);
+ }
+ printf("GL_RENDERER = %s\n",(const char *) glGetString(GL_RENDERER));
+
+ GetExtensionFuncs();
+
+ FragShader = glCreateShader_func(GL_FRAGMENT_SHADER);
+ LoadAndCompileShader(FragShader, fragShaderText);
+
+ VertShader = glCreateShader_func(GL_VERTEX_SHADER);
+ LoadAndCompileShader(VertShader, vertShaderText);
+
+ Program = glCreateProgram_func();
+ glAttachShader_func(Program, FragShader);
+ glAttachShader_func(Program, VertShader);
+ glLinkProgram_func(Program);
+ CheckLink(Program);
+ glUseProgram_func(Program);
+
+ uViewportInv = glGetUniformLocation_func(Program, "viewportInv");
+
+ glUseProgram_func(0);
+
+ glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+ glutInit(&argc, argv);
+ glutInitWindowSize(WinWidth, WinHeight);
+ glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
+ Win = glutCreateWindow(argv[0]);
+ glutReshapeFunc(Reshape);
+ glutKeyboardFunc(Key);
+ glutSpecialFunc(SpecialKey);
+ glutDisplayFunc(Redisplay);
+ Init();
+ glutMainLoop();
+ return 0;
+}
+
+
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