Added world to screen conversion

- Added function WorldToScreen(...).
- Added world to screen example.
- Review GetMouseRay() comment.
- Removed deprecated lighting functions from raylib header.

examples/core_world_screen.c

@@ -0,0 +1,77 @@
+/*******************************************************************************************
+*
+*   raylib [core] example - World to screen
+*
+*   This example has been created using raylib 1.3 (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
+*
+*   Copyright (c) 2015 Ramon Santamaria (@raysan5)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+
+int main()
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    int screenWidth = 800;
+    int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [core] example - 3d camera free");
+
+    // Define the camera to look into our 3d world
+    Camera camera = {{ 0.0, 10.0, 10.0 }, { 0.0, 0.0, 0.0 }, { 0.0, 1.0, 0.0 }};
+
+    Vector3 cubePosition = { 0.0, 0.0, 0.0 };
+    
+    Vector2 cubeScreenPosition;
+    
+    SetCameraMode(CAMERA_FREE);         // Set a free camera mode
+    SetCameraPosition(camera.position); // Set internal camera position to match our camera position
+    SetCameraTarget(camera.target);     // Set internal camera target to match our camera target
+
+    SetTargetFPS(60);                   // Set our game to run at 60 frames-per-second
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())        // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        UpdateCamera(&camera);          // Update internal camera and our camera
+        
+        // Calculate cube screen space position (with a little offset to be in top)
+        cubeScreenPosition = WorldToScreen((Vector3){cubePosition.x, cubePosition.y + 2.5f, cubePosition.z}, camera);
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            Begin3dMode(camera);
+
+                DrawCube(cubePosition, 2, 2, 2, RED);
+                DrawCubeWires(cubePosition, 2, 2, 2, MAROON);
+
+                DrawGrid(10.0, 1.0);
+
+            End3dMode();
+            
+            DrawText("Enemy: 100 / 100", cubeScreenPosition.x - MeasureText("Enemy: 100 / 100", 20) / 2, cubeScreenPosition.y, 20, BLACK);
+            DrawText("Text is always on top of the cube", (screenWidth - MeasureText("Text is always on top of the cube", 20)) / 2, 25, 20, GRAY);
+            
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}