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82 lines
2.1 KiB
C
82 lines
2.1 KiB
C
/*
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OpenGL cannot calculate diffuse shadows unless you do a lot of work:
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http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-16-shadow-mapping/
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http://http.developer.nvidia.com/GPUGems/gpugems_ch12.html
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This example only illustrates that the top triangle,
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which should act as an umbrella and cover all light coming from +y infinity
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from the bottom one, does nothing, and so both have the same color.
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*/
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#include <stdlib.h>
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#include <GL/gl.h>
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#include <GL/glu.h>
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#include <GL/glut.h>
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static void init(void) {
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GLfloat light0_diffuse[] = {1.0, 1.0, 1.0, 1.0};
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GLfloat light0_position[] = {0.0, 1.0, 0.0, 0.0};
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glClearColor(0.0, 0.0, 0.0, 0.0);
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glShadeModel(GL_SMOOTH);
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glLightfv(GL_LIGHT0, GL_POSITION, light0_position);
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glLightfv(GL_LIGHT0, GL_DIFFUSE, light0_diffuse);
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glEnable(GL_LIGHTING);
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glEnable(GL_LIGHT0);
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glColorMaterial(GL_FRONT, GL_DIFFUSE);
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glEnable(GL_COLOR_MATERIAL);
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glEnable(GL_NORMALIZE);
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}
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static void draw_rectangle(void) {
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glBegin(GL_TRIANGLES);
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glVertex3f(0.0f, 1.0f, 0.0f);
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glVertex3f(-1.0f, -1.0f, 0.0f);
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glVertex3f(1.0f, -1.0f, 0.0f);
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glEnd();
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}
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static void display(void) {
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glClear(GL_COLOR_BUFFER_BIT);
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glColor3f(1.0, 1.0, 1.0);
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/* Bottom triangle. */
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glPushMatrix();
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glRotatef(45.0, -1.0, 0.0, 0.0);
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draw_rectangle();
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glPopMatrix();
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/* Top triangle triangle, 2x as large to cover the light. */
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glPushMatrix();
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glTranslatef(0.0, 2.5, 0.0);
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glScalef(2.0, 2.0, 2.0);
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glRotatef(45.0, -1.0, 0.0, 0.0);
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draw_rectangle();
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glPopMatrix();
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glFlush();
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}
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static void reshape(int w, int h) {
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glViewport(0, 0, w, h);
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glMatrixMode(GL_PROJECTION);
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glLoadIdentity();
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glOrtho(-4.0, 4.0, -2.0, 4.0, -4.0, 4.0);
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glMatrixMode(GL_MODELVIEW);
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glLoadIdentity();
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}
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int main(int argc, char** argv) {
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glutInit(&argc, argv);
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glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
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glutInitWindowSize(500, 500);
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glutInitWindowPosition(100, 100);
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glutCreateWindow(argv[0]);
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init();
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glutDisplayFunc(display);
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glutReshapeFunc(reshape);
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glutMainLoop();
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return EXIT_SUCCESS;
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}
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