--- /dev/null
+/*
+ * Copyright (C) 2009 Chia-I Wu <olv@0xlab.org>
+ *
+ * Based on eglgears by
+ * Copyright (C) 1999-2001 Brian Paul All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+#include <assert.h>
+
+#include <GLES/gl.h>
+#include "winsys.h"
+
+#ifndef M_PI
+#define M_PI 3.14159265
+#endif
+
+
+struct gear {
+ GLuint vbo;
+ GLfloat *vertices;
+ GLsizei stride;
+
+ GLint num_teeth;
+};
+
+static GLfloat view_rotx = 20.0, view_roty = 30.0, view_rotz = 0.0;
+static struct gear gears[3];
+static GLfloat angle = 0.0;
+
+/*
+ * Initialize a gear wheel.
+ *
+ * Input: gear - gear to initialize
+ * inner_radius - radius of hole at center
+ * outer_radius - radius at center of teeth
+ * width - width of gear
+ * teeth - number of teeth
+ * tooth_depth - depth of tooth
+ */
+static void
+init_gear(struct gear *gear, GLfloat inner_radius, GLfloat outer_radius,
+ GLfloat width, GLint teeth, GLfloat tooth_depth)
+{
+ GLfloat r0, r1, r2;
+ GLfloat a0, da;
+ GLint verts_per_tooth, total_verts, total_size;
+ GLint count, i;
+ GLfloat *verts;
+
+ r0 = inner_radius;
+ r1 = outer_radius - tooth_depth / 2.0;
+ r2 = outer_radius + tooth_depth / 2.0;
+
+ a0 = 2.0 * M_PI / teeth;
+ da = a0 / 4.0;
+
+ gear->vbo = 0;
+ gear->vertices = NULL;
+ gear->stride = sizeof(GLfloat) * 6; /* XYZ + normal */
+ gear->num_teeth = teeth;
+
+ verts_per_tooth = 10 + 4;
+ total_verts = teeth * verts_per_tooth;
+ total_size = total_verts * gear->stride;
+
+ verts = malloc(total_size);
+ if (!verts) {
+ printf("failed to allocate vertices\n");
+ return;
+ }
+
+#define GEAR_VERT(r, n, sign) \
+ do { \
+ verts[count * 6 + 0] = (r) * vx[n]; \
+ verts[count * 6 + 1] = (r) * vy[n]; \
+ verts[count * 6 + 2] = (sign) * width * 0.5; \
+ verts[count * 6 + 3] = normal[0]; \
+ verts[count * 6 + 4] = normal[1]; \
+ verts[count * 6 + 5] = normal[2]; \
+ count++; \
+ } while (0)
+
+ count = 0;
+ for (i = 0; i < teeth; i++) {
+ GLfloat normal[3];
+ GLfloat vx[5], vy[5];
+ GLfloat u, v;
+
+ normal[0] = 0.0;
+ normal[1] = 0.0;
+ normal[2] = 0.0;
+
+ vx[0] = cos(i * a0 + 0 * da);
+ vy[0] = sin(i * a0 + 0 * da);
+ vx[1] = cos(i * a0 + 1 * da);
+ vy[1] = sin(i * a0 + 1 * da);
+ vx[2] = cos(i * a0 + 2 * da);
+ vy[2] = sin(i * a0 + 2 * da);
+ vx[3] = cos(i * a0 + 3 * da);
+ vy[3] = sin(i * a0 + 3 * da);
+ vx[4] = cos(i * a0 + 4 * da);
+ vy[4] = sin(i * a0 + 4 * da);
+
+ /* outward faces of a tooth, 10 verts */
+ normal[0] = vx[0];
+ normal[1] = vy[0];
+ GEAR_VERT(r1, 0, 1);
+ GEAR_VERT(r1, 0, -1);
+
+ u = r2 * vx[1] - r1 * vx[0];
+ v = r2 * vy[1] - r1 * vy[0];
+ normal[0] = v;
+ normal[1] = -u;
+ GEAR_VERT(r2, 1, 1);
+ GEAR_VERT(r2, 1, -1);
+
+ normal[0] = vx[0];
+ normal[1] = vy[0];
+ GEAR_VERT(r2, 2, 1);
+ GEAR_VERT(r2, 2, -1);
+
+ u = r1 * vx[3] - r2 * vx[2];
+ v = r1 * vy[3] - r2 * vy[2];
+ normal[0] = v;
+ normal[1] = -u;
+ GEAR_VERT(r1, 3, 1);
+ GEAR_VERT(r1, 3, -1);
+
+ normal[0] = vx[0];
+ normal[1] = vy[0];
+ GEAR_VERT(r1, 4, 1);
+ GEAR_VERT(r1, 4, -1);
+
+ /* inside radius cylinder, 4 verts */
+ normal[0] = -vx[4];
+ normal[1] = -vy[4];
+ GEAR_VERT(r0, 4, 1);
+ GEAR_VERT(r0, 4, -1);
+
+ normal[0] = -vx[0];
+ normal[1] = -vy[0];
+ GEAR_VERT(r0, 0, 1);
+ GEAR_VERT(r0, 0, -1);
+
+ assert(count % verts_per_tooth == 0);
+ }
+ assert(count == total_verts);
+#undef GEAR_VERT
+
+ gear->vertices = verts;
+
+ /* setup VBO */
+ glGenBuffers(1, &gear->vbo);
+ if (gear->vbo) {
+ glBindBuffer(GL_ARRAY_BUFFER, gear->vbo);
+ glBufferData(GL_ARRAY_BUFFER, total_size, verts, GL_STATIC_DRAW);
+ }
+}
+
+
+static void
+draw_gear(const struct gear *gear)
+{
+ GLint i;
+
+ if (!gear->vbo && !gear->vertices) {
+ printf("nothing to be drawn\n");
+ return;
+ }
+
+ if (gear->vbo) {
+ glBindBuffer(GL_ARRAY_BUFFER, gear->vbo);
+ glVertexPointer(3, GL_FLOAT, gear->stride, (const GLvoid *) 0);
+ glNormalPointer(GL_FLOAT, gear->stride, (const GLvoid *) (sizeof(GLfloat) * 3));
+ } else {
+ glBindBuffer(GL_ARRAY_BUFFER, 0);
+ glVertexPointer(3, GL_FLOAT, gear->stride, gear->vertices);
+ glNormalPointer(GL_FLOAT, gear->stride, gear->vertices + 3);
+ }
+
+ glEnableClientState(GL_VERTEX_ARRAY);
+
+ for (i = 0; i < gear->num_teeth; i++) {
+ const GLint base = (10 + 4) * i;
+ GLushort indices[7];
+
+ glShadeModel(GL_FLAT);
+
+ /* front face */
+ indices[0] = base + 12;
+ indices[1] = base + 0;
+ indices[2] = base + 2;
+ indices[3] = base + 4;
+ indices[4] = base + 6;
+ indices[5] = base + 8;
+ indices[6] = base + 10;
+
+ glNormal3f(0.0, 0.0, 1.0);
+ glDrawElements(GL_TRIANGLE_FAN, 7, GL_UNSIGNED_SHORT, indices);
+
+ /* back face */
+ indices[0] = base + 13;
+ indices[1] = base + 11;
+ indices[2] = base + 9;
+ indices[3] = base + 7;
+ indices[4] = base + 5;
+ indices[5] = base + 3;
+ indices[6] = base + 1;
+
+ glNormal3f(0.0, 0.0, -1.0);
+ glDrawElements(GL_TRIANGLE_FAN, 7, GL_UNSIGNED_SHORT, indices);
+
+ glEnableClientState(GL_NORMAL_ARRAY);
+
+ /* outward face of a tooth */
+ glDrawArrays(GL_TRIANGLE_STRIP, base, 10);
+
+ /* inside radius cylinder */
+ glShadeModel(GL_SMOOTH);
+ glDrawArrays(GL_TRIANGLE_STRIP, base + 10, 4);
+
+ glDisableClientState(GL_NORMAL_ARRAY);
+ }
+
+ glDisableClientState(GL_VERTEX_ARRAY);
+}
+
+
+static void
+gears_draw(void *data)
+{
+ static const GLfloat red[4] = { 0.8, 0.1, 0.0, 1.0 };
+ static const GLfloat green[4] = { 0.0, 0.8, 0.2, 1.0 };
+ static const GLfloat blue[4] = { 0.2, 0.2, 1.0, 1.0 };
+
+ glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+
+ glPushMatrix();
+ glRotatef(view_rotx, 1.0, 0.0, 0.0);
+ glRotatef(view_roty, 0.0, 1.0, 0.0);
+ glRotatef(view_rotz, 0.0, 0.0, 1.0);
+
+ glPushMatrix();
+ glTranslatef(-3.0, -2.0, 0.0);
+ glRotatef(angle, 0.0, 0.0, 1.0);
+
+ glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, red);
+ draw_gear(&gears[0]);
+
+ glPopMatrix();
+
+ glPushMatrix();
+ glTranslatef(3.1, -2.0, 0.0);
+ glRotatef(-2.0 * angle - 9.0, 0.0, 0.0, 1.0);
+
+ glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, green);
+ draw_gear(&gears[1]);
+
+ glPopMatrix();
+
+ glPushMatrix();
+ glTranslatef(-3.1, 4.2, 0.0);
+ glRotatef(-2.0 * angle - 25.0, 0.0, 0.0, 1.0);
+
+ glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE, blue);
+ draw_gear(&gears[2]);
+
+ glPopMatrix();
+
+ glPopMatrix();
+
+ /* advance rotation for next frame */
+ angle += 0.5; /* 0.5 degree per frame */
+ if (angle > 3600.0)
+ angle -= 3600.0;
+}
+
+
+static void gears_fini(void)
+{
+ GLint i;
+ for (i = 0; i < 3; i++) {
+ struct gear *gear = &gears[i];
+ if (gear->vbo) {
+ glDeleteBuffers(1, &gear->vbo);
+ gear->vbo = 0;
+ }
+ if (gear->vertices) {
+ free(gear->vertices);
+ gear->vertices = NULL;
+ }
+ }
+}
+
+
+static void gears_init(void)
+{
+ static const GLfloat pos[4] = { 5.0, 5.0, 10.0, 0.0 };
+
+ glLightfv(GL_LIGHT0, GL_POSITION, pos);
+ glEnable(GL_CULL_FACE);
+ glEnable(GL_LIGHTING);
+ glEnable(GL_LIGHT0);
+ glEnable(GL_DEPTH_TEST);
+ glEnable(GL_NORMALIZE);
+
+ init_gear(&gears[0], 1.0, 4.0, 1.0, 20, 0.7);
+ init_gear(&gears[1], 0.5, 2.0, 2.0, 10, 0.7);
+ init_gear(&gears[2], 1.3, 2.0, 0.5, 10, 0.7);
+}
+
+
+/* new window size or exposure */
+static void
+gears_reshape(int width, int height)
+{
+ GLfloat h = (GLfloat) height / (GLfloat) width;
+
+ glViewport(0, 0, (GLint) width, (GLint) height);
+
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ glFrustumf(-1.0, 1.0, -h, h, 5.0, 60.0);
+
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+ glTranslatef(0.0, 0.0, -40.0);
+}
+
+
+static void gears_run(void)
+{
+ winsysRun(5.0, gears_draw, NULL);
+}
+
+
+int
+main(int argc, char *argv[])
+{
+ EGLint width, height;
+
+ if (!winsysInitScreen())
+ exit(1);
+ winsysQueryScreenSize(&width, &height);
+
+ gears_init();
+ gears_reshape(width, height);
+ gears_run();
+ gears_fini();
+
+ winsysFiniScreen();
+
+ return 0;
+}
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