Allow changing the fov and render distance

src/JGL.cpp

@@ -529,7 +529,46 @@ namespace JGL {
 
     }
 
+    //The 3D projection.
+    std::vector<GLfloat> perspective(float fov, float aspect, float nearPlane, float farPlane) {
+        std::vector<float> result(16);
+        float f = 1.0f / tan(fov * 0.5f * M_PI / 180.0f);
+        result[0] = f / aspect;
+        result[5] = f;
+        result[10] = (farPlane + nearPlane) / (nearPlane - farPlane);
+        result[11] = -1.0f;
+        result[14] = (2.0f * farPlane * nearPlane) / (nearPlane - farPlane);
+        return result;
+    }
+
+    bool j3d_initialized = false;
+    float j3d_far_plane = 0;
+    float j3d_fov = 0;
+
+    void J3D::Init(const J3ML::LinearAlgebra::Vector2& window_size, float fov, float far_plane) {
+        wS = window_size;
+        j3d_far_plane = far_plane;
+        j3d_fov = fov;
+        j3d_initialized = true;
+    }
+
+    void J3D::ChangeFOV(float fov) {
+        j3d_fov = fov;
+    }
+
+    void J3D::ChangeFarPlane(float far_plane) {
+        j3d_far_plane = far_plane;
+    }
+
     void J3D::Begin() {
+        if (!j3d_initialized)
+            throw std::runtime_error("You have to run J3D::Init before rendering 3D elements.");
+
+        auto aspect = (float) wS.x / (float) wS.y;
+        glMatrixMode(GL_PROJECTION);
+        glLoadIdentity();
+        glMultMatrixf(perspective(j3d_fov, aspect, 0.001, j3d_far_plane).data());
+        glMatrixMode(GL_MODELVIEW);
 
         //Get what the draw color was before we did anything.
         glGetFloatv(GL_CURRENT_COLOR, oldColor);