Demos (master): drawstencil: test writing stencil image with fragment shader
Brian Paul
brianp at kemper.freedesktop.org
Sun Apr 10 23:01:19 UTC 2011
Module: Demos
Branch: master
Commit: e0007e3ea40607b70ee3135132e1aa58800e2f2e
URL: http://cgit.freedesktop.org/mesa/demos/commit/?id=e0007e3ea40607b70ee3135132e1aa58800e2f2e
Author: Brian Paul <brianp at vmware.com>
Date: Sun Apr 10 16:58:22 2011 -0600
drawstencil: test writing stencil image with fragment shader
---
src/tests/CMakeLists.txt | 1 +
src/tests/Makefile.am | 1 +
src/tests/drawstencil.c | 224 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 226 insertions(+), 0 deletions(-)
diff --git a/src/tests/CMakeLists.txt b/src/tests/CMakeLists.txt
index fb20c04..5377483 100644
--- a/src/tests/CMakeLists.txt
+++ b/src/tests/CMakeLists.txt
@@ -54,6 +54,7 @@ set (targets
#debugger
drawbuffers2
drawbuffers
+ drawstencil
exactrast
ext422square
fbotest1
diff --git a/src/tests/Makefile.am b/src/tests/Makefile.am
index 0d7c411..632f406 100644
--- a/src/tests/Makefile.am
+++ b/src/tests/Makefile.am
@@ -81,6 +81,7 @@ noinst_PROGRAMS = \
cylwrap \
drawbuffers \
drawbuffers2 \
+ drawstencil \
exactrast \
ext422square \
floattex \
diff --git a/src/tests/drawstencil.c b/src/tests/drawstencil.c
new file mode 100644
index 0000000..0bc57dc
--- /dev/null
+++ b/src/tests/drawstencil.c
@@ -0,0 +1,224 @@
+/**
+ * Draw stencil region
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <GL/glew.h>
+#include <GL/glut.h>
+
+static int Win;
+static int WinWidth = 600, WinHeight = 200;
+static GLfloat Xrot = 0.0, Yrot = 0.0;
+
+#define WIDTH 256
+#define HEIGHT 150
+
+static GLubyte Image[HEIGHT][WIDTH];
+
+
+static void
+DrawStencilPixels(GLint x, GLint y, GLsizei w, GLsizei h,
+ const GLubyte *stencil)
+{
+ /* This program is run eight times, once for each stencil bit.
+ * The stencil values to draw are found in an 8-bit alpha texture.
+ * We read the texture/stencil value and test if bit 'b' is set.
+ * If the bit is set, result.A will be non-zero. Finally, use
+ * alpha test and stencil test to update the stencil buffer.
+ *
+ * The basic algorithm for checking if a bit is set is:
+ * if (is_odd(value / (1 << bit)))
+ * result is one (or non-zero).
+ * else
+ * result is zero.
+ * The program parameter contains two values:
+ * parm.x = 255 / (1 << bit)
+ * parm.y = 0.5
+ */
+ static const char *program =
+ "!!ARBfp1.0\n"
+ "PARAM parm = program.local[0]; \n"
+ "TEMP t; \n"
+ "TEX t, fragment.texcoord[0], texture[0], RECT; \n"
+ "# t = t * 255 / bit \n"
+ "MUL t.x, t.a, parm.x; \n"
+ "# t = (int) t \n"
+ "FRC t.y, t.x; \n"
+ "SUB t.x, t.x, t.y; \n"
+ "# t = 5 * 0.5 \n"
+ "MUL t.x, t.x, parm.y; \n"
+ "# alpha = frac(t) \n"
+ "FRC result.color, t.x; \n"
+ "END \n";
+ GLuint prog;
+ GLint bit;
+
+ glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+ glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_ALPHA, w, h, 0,
+ GL_ALPHA, GL_UNSIGNED_BYTE, stencil);
+ glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+ glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+
+ glGenProgramsARB(1, &prog);
+ glBindProgramARB(GL_FRAGMENT_PROGRAM_ARB, prog);
+ glProgramStringARB(GL_FRAGMENT_PROGRAM_ARB, GL_PROGRAM_FORMAT_ASCII_ARB,
+ strlen(program), (const GLubyte *) program);
+ glEnable(GL_FRAGMENT_PROGRAM_ARB);
+
+ glPushMatrix();
+ glTranslatef(x, y, 0);
+
+ glEnable(GL_ALPHA_TEST);
+ glAlphaFunc(GL_GREATER, 0.0);
+
+ glEnable(GL_STENCIL_TEST);
+ glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
+
+ for (bit = 0; bit < 8; bit++) {
+ GLuint mask = 1 << bit;
+ glStencilFunc(GL_ALWAYS, 255/*mask*/, mask);
+ glStencilMask(mask);
+
+ glProgramLocalParameter4fARB(GL_FRAGMENT_PROGRAM_ARB, 0,
+ // 1.0 / bit, 0.5, 0.0, 0.0);
+ 255.0 / mask, 0.5, 0.0, 0.0);
+
+
+ glBegin(GL_TRIANGLE_FAN);
+ glTexCoord2f(0, 0); glVertex2f(0, 0);
+ glTexCoord2f(w, 0); glVertex2f(w, 0);
+ glTexCoord2f(w, h); glVertex2f(w, h);
+ glTexCoord2f(0, h); glVertex2f(0, h);
+ glEnd();
+ }
+
+ glPopMatrix();
+
+ glDisable(GL_FRAGMENT_PROGRAM_ARB);
+ glDisable(GL_ALPHA_TEST);
+ glDisable(GL_STENCIL_TEST);
+}
+
+
+
+static void
+Draw(void)
+{
+ GLint x0 = 5, y0= 5, x1 = 10 + WIDTH, y1 = 5;
+ GLubyte tmp[HEIGHT][WIDTH];
+ GLint max, i, j;
+
+ glClearColor(0.2, 0.2, 0.8, 0.0);
+ glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
+
+#if 0
+ DrawStencilPixels(x0, y0, WIDTH, HEIGHT, (GLubyte*) Image);
+#else
+ glWindowPos2i(x0, y0);
+ glDrawPixels(WIDTH, HEIGHT, GL_STENCIL_INDEX,
+ GL_UNSIGNED_BYTE, (GLubyte*) Image);
+#endif
+
+ glReadPixels(x0, y0, WIDTH, HEIGHT, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, tmp);
+
+ max = 0;
+ for (i = 0; i < HEIGHT; i++) {
+ for (j = 0; j < WIDTH; j++) {
+ if (tmp[i][j] > max)
+ max = tmp[i][j];
+ }
+ }
+ printf("max = %d\n", max);
+
+ glWindowPos2i(x1, y1);
+ glDrawPixels(WIDTH, HEIGHT, GL_LUMINANCE, GL_UNSIGNED_BYTE, tmp);
+
+ glutSwapBuffers();
+}
+
+
+static void
+Reshape(int width, int height)
+{
+ WinWidth = width;
+ WinHeight = height;
+ glViewport(0, 0, width, height);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ glOrtho(0, width, 0, height, -1, 1);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+}
+
+
+static void
+Key(unsigned char key, int x, int y)
+{
+ (void) x;
+ (void) y;
+ switch (key) {
+ case 27:
+ glutDestroyWindow(Win);
+ exit(0);
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void
+SpecialKey(int key, int x, int y)
+{
+ const GLfloat step = 3.0;
+ (void) x;
+ (void) y;
+ switch (key) {
+ case GLUT_KEY_UP:
+ Xrot -= step;
+ break;
+ case GLUT_KEY_DOWN:
+ Xrot += step;
+ break;
+ case GLUT_KEY_LEFT:
+ Yrot -= step;
+ break;
+ case GLUT_KEY_RIGHT:
+ Yrot += step;
+ break;
+ }
+ glutPostRedisplay();
+}
+
+
+static void
+Init(void)
+{
+ int i, j;
+ for (i = 0; i < HEIGHT; i++) {
+ for (j = 0; j < WIDTH; j++) {
+ Image[i][j] = j;
+ }
+ }
+}
+
+
+int
+main(int argc, char *argv[])
+{
+ glutInit(&argc, argv);
+ glutInitWindowSize(WinWidth, WinHeight);
+ glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_STENCIL);
+ Win = glutCreateWindow(argv[0]);
+ glewInit();
+ glutReshapeFunc(Reshape);
+ glutKeyboardFunc(Key);
+ glutSpecialFunc(SpecialKey);
+ glutDisplayFunc(Draw);
+ Init();
+ glutMainLoop();
+ return 0;
+}
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