From df6a25599abac84f0f736b3029024cdd500bc106 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Stensg=C3=A5rd?= <mastensg@ping.uio.no>
Date: Mon, 18 Oct 2010 23:31:35 +0200
Subject: Weird effect.

---
 ray.c | 177 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)
 create mode 100644 ray.c

(limited to 'ray.c')

diff --git a/ray.c b/ray.c
new file mode 100644
index 0000000..f96f5f0
--- /dev/null
+++ b/ray.c
@@ -0,0 +1,177 @@
+#include <GL/gl.h>
+#include <GL/glu.h>
+#include <GL/glut.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+
+#define WIDTH 1080
+#define HEIGHT 1080
+#define BUFFER_SIZE (WIDTH * HEIGHT * 4)
+
+#define LENGTH(array)   (sizeof(array) / sizeof(array[0]))
+#define MAX(x, y) (x > y ? x : y)
+#define MIN(x, y) (x < y ? x : y)
+#define POW2(x) ((x) * (x))
+#define POW3(x) ((x) * (x) * (x))
+#define POW4(x) ((x) * (x) * (x) * (x))
+#define POW5(x) ((x) * (x) * (x) * (x) * (x))
+
+typedef struct {
+    float position[3];
+    float radius;
+    float diffuse[3];
+} Object;
+
+typedef struct {
+    float position[3];
+    float diffuse[3];
+} Light;
+
+static Object objects[2] = {{.position={1.5, 0, -20}, .radius=.1, .diffuse={0, 0, .3}},
+                            {.position={-1.5, 0, -30}, .radius=.1, .diffuse={0, 0, .3}}};
+static Light lights[1] = {{.position={0, 2, -4}, .diffuse={0, .7, .7}}};
+static unsigned char buffer[BUFFER_SIZE];
+
+static float
+dot(float x[3], float y[3]) {
+    return x[0] * y[0] + x[1] * y[1] + x[2] * y[2];
+}
+
+static void
+normalize(float x[3]) {
+    float len;
+    int i;
+
+    len = sqrt(dot(x, x));
+
+    for(i = 0; i < 3; ++i)
+        x[i] /= len;
+}
+
+static void
+trace(float s[3], float d[3], float pixel[3], int N) {
+    int i, j;
+    float D;
+    float l[3];
+    float n[3];
+    float t;
+    float v[3];
+    float vd, vv;
+    float y[3];
+    Object *object = objects;
+    Light *light = lights;
+
+    for(j = 0; j < LENGTH(objects); ++j) {
+        object = &objects[j];
+
+        for(i = 0; i < 3; ++i)
+            v[i] = s[i] - object->position[i];
+
+        vd = dot(v, d);
+        vv = dot(v, v);
+
+        D = POW2(2 * vd) - 4 * (vv - POW2(object->radius));
+
+        if(D < 0) {
+            pixel[0] += .3;
+            pixel[1] += .15;
+            pixel[2] += .075;
+        } else {
+
+            t = MIN(-vd + sqrt(D), -vd - sqrt(D));
+
+            for(i = 0; i < 3; ++i) {
+                y[i] = s[i] + t * d[i];
+                n[i] = y[i] - object->position[i];
+                l[i] = light->position[i] - object->position[i];
+            }
+
+            normalize(n);
+            normalize(l);
+
+            for(i = 0; i < 3; ++i) {
+                n[i] = (object->diffuse[i] + light->diffuse[i]) * dot(n, l);
+                //n[i] = object->diffuse[i];
+                pixel[i] += n[i];
+            }
+
+            if(N)
+                trace(y, n, pixel, N - 1);
+        }
+    }
+}
+
+static void
+display(void) {
+    int i, j;
+    float x, y;
+    float s[3] = {0, 0, 1};
+    float d[3];
+    float pixel[3];
+
+    memset(buffer, '\0', sizeof(buffer));
+
+    for(i = 0; i < BUFFER_SIZE; i += 4) {
+        x = (i / 4) % WIDTH - WIDTH / 2;
+        y = (i / 4) / WIDTH - HEIGHT / 2;
+
+        d[0] = x / (WIDTH / 2);
+        d[1] = y / (HEIGHT / 2);
+        d[2] = -1;
+
+        memset(pixel, '\0', sizeof(pixel));
+        trace(s, d, pixel, 0);
+
+        //printf("%f %f %f\n", pixel[0], pixel[1], pixel[2]);
+
+        for(j = 0; j < 3; ++j)
+            buffer[i + j] = MIN(255 * pixel[j], 255);
+    }
+
+    glDrawPixels(WIDTH, HEIGHT, GL_BGRA, GL_UNSIGNED_BYTE, buffer);
+
+    glutSwapBuffers();
+}
+
+static void
+reshape(int w, int h) {
+    glViewport(0, 0, w, h);
+}
+
+static void
+keyboard(unsigned char key, int x, int y) {
+    if (key == 27)
+        exit(0);
+}
+
+static int
+init(int argc, char **argv, int w, int h) {
+    glutInit(&argc, argv);
+
+    glutInitWindowPosition(0, 0);
+    glutInitWindowSize(w, h);
+    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
+    glutCreateWindow(argv[0]);
+
+    glDepthMask(0);
+    glDisable(GL_DEPTH_TEST);
+    glDisable(GL_BLEND);
+
+    return 0;
+}
+
+int
+main(int argc, char **argv) {
+    if (init(argc, argv, WIDTH, HEIGHT))
+        return 1;
+
+    glutDisplayFunc(display);
+    glutReshapeFunc(reshape);
+    glutKeyboardFunc(keyboard);
+
+    glutMainLoop();
+
+    return 0;
+}
-- 
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