Add spherical mapping for UV Textures.

source/pattern/texturemap.h

@@ -0,0 +1,89 @@
+/*
+ *  DoRayMe - a quick and dirty Raytracer
+ *  Texture Map header
+ *
+ *  Created by Manoël Trapier
+ *  Copyright (c) 2020 986-Studio.
+ *
+ */
+
+#ifndef DORAYME_TEXTUREMAP_H
+#define DORAYME_TEXTUREMAP_H
+
+#include <math.h>
+#include <tuple.h>
+#include <uv_pattern.h>
+#include <colour.h>
+enum TextureMapType
+{
+    SPHERICAL_MAP,
+    PLANAR_MAP,
+    CYLINDRICAL_MAP,
+};
+
+class TextureMap : public Pattern
+{
+private:
+    TextureMapType type;
+    UVPattern *pattern;
+public:
+    TextureMap(TextureMapType type, UVPattern *pattern) : Pattern(Colour(0, 0, 0), Colour(0, 0, 0)),
+                                                          type(type), pattern(pattern) { };
+
+    static void sphericalMap(Tuple point, double &u, double &v) {
+        /* First compute the azimuthal angle
+         * -π < theta <= π
+         * angle increases clockwise as viewed from above,
+         * which is opposite of what we want, but we'll fix it later.
+         */
+        double theta = atan2(point.x, point.z);
+
+        /* vec is the vector pointing from the sphere's origin (the world origin)
+         * to the point, which will also happen to be exactly equal to the sphere's
+         * radius.
+         */
+        Tuple vec = Vector(point.x, point.y, point.z);
+        double radius = vec.magnitude();
+
+        /* Let's compute the polar angle
+         * 0 <= phi <= π
+         */
+        double phi = acos(point.y / radius);
+
+        /* -0.5 < raw_u <= 0.5 */
+        double raw_u = theta / (2 * M_PI);
+
+        /* 0 <= u < 1
+         * here's also where we fix the direction of u. Subtract it from 1,
+         * so that it increases counterclockwise as viewed from above.
+         */
+        u = 1 - (raw_u + 0.5);
+
+        /* We want v to be 0 at the south pole of the sphere,
+         * and 1 at the north pole, so we have to "flip it over"
+         * by subtracting it from 1.
+         */
+        v = 1 - phi / M_PI;
+    }
+
+    Colour patternAt(Tuple point)
+    {
+        double u,v;
+        switch(this->type)
+        {
+        default:
+        case SPHERICAL_MAP:
+            this->sphericalMap(point, u, v);
+            break;
+        }
+
+        return this->pattern->uvPatternAt(u, v);
+    }
+
+    void dumpMe(FILE *fp) {
+        fprintf(fp, "\"Type\": \"TextureMap\",\n");
+        Pattern::dumpMe(fp);
+    }
+};
+
+#endif /* DORAYME_TEXTUREMAP_H */