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Diffstat (limited to 'progs/glsl/points.c')
| -rw-r--r-- | progs/glsl/points.c | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/progs/glsl/points.c b/progs/glsl/points.c new file mode 100644 index 00000000000..392dc4db853 --- /dev/null +++ b/progs/glsl/points.c @@ -0,0 +1,260 @@ +/** + * 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" +#include "shaderutil.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 +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"; + + if (!ShadersSupported()) + exit(1); + + GetExtensionFuncs(); + + VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText); + FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText); + Program = LinkShaders(VertShader, FragShader); + + 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; +} + + |