Added physics engine-module and example

- Added new physics engine-module with four new data types: Physics,
Transform, Rigidbody and Collider. This library contains functions to
apply physics calculations to a position vector calculating collisions
automatically.

- Fixed some writing mistakes of lighting module.

examples/physics_basic_rigidbody.c

@@ -0,0 +1,144 @@
+/*******************************************************************************************
+*
+*   raylib [physics] example - Basic rigidbody
+*
+*   Welcome to raylib!
+*
+*   To test examples, just press F6 and execute raylib_compile_execute script
+*   Note that compiled executable is placed in the same folder as .c file
+*
+*   You can find all basic examples on C:\raylib\raylib\examples folder or
+*   raylib official webpage: www.raylib.com
+*
+*   Enjoy using raylib. :)
+*
+*   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"
+
+#define OBJECT_SIZE 50
+#define PLAYER_INDEX 0
+
+int main()
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    int screenWidth = 800;
+    int screenHeight = 450;
+    
+    InitWindow(screenWidth, screenHeight, "raylib [physics] example - basic rigidbody");
+    SetTargetFPS(60);   // Enable v-sync
+    InitPhysics();      // Initialize internal physics values   (max rigidbodies/colliders available: 1024)
+    
+    // Physics initialization
+    Physics worldPhysics = {true, false, (Vector2){0, -9.81f}};
+    
+    // Set internal physics settings
+    SetPhysics(worldPhysics);
+    
+    // Object initialization
+    Transform player = (Transform){(Vector2){(screenWidth - OBJECT_SIZE) / 2, (screenHeight - OBJECT_SIZE) / 2}, 0.0f, (Vector2){OBJECT_SIZE, OBJECT_SIZE}};
+    AddCollider(PLAYER_INDEX, (Collider){true, RectangleCollider, (Rectangle){player.position.x, player.position.y, player.scale.x, player.scale.y}, 0});
+    AddRigidbody(PLAYER_INDEX, (Rigidbody){true, 1.0f, (Vector2){0, 0}, (Vector2){0, 0}, false, false, true, 0.5f, 1.0f});
+    
+    // Floor initialization 
+    // NOTE: floor doesn't need a rigidbody because it's a static physic object, just a collider to collide with other dynamic colliders (with rigidbody)
+    Transform floor = (Transform){(Vector2){0, screenHeight * 0.8f}, 0.0f, (Vector2){screenWidth, screenHeight * 0.2f}};
+    AddCollider(PLAYER_INDEX + 1, (Collider){true, RectangleCollider, (Rectangle){floor.position.x, floor.position.y, floor.scale.x, floor.scale.y}, 0});
+    
+    // Object properties initialization
+    float moveSpeed = 6.0f;
+    float jumpForce = 4.5f;
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        
+        // Update object physics 
+        // NOTE: all physics detections and reactions are calculated in ApplyPhysics() function (You will live happier :D)
+        ApplyPhysics(PLAYER_INDEX, &player.position);
+        
+        // Check jump button input
+        if(IsKeyDown(KEY_SPACE) && GetRigidbody(PLAYER_INDEX).isGrounded)
+        {
+            // Reset object Y velocity to avoid double jumping cases but keep the same X velocity that it already has
+            SetRigidbodyVelocity(PLAYER_INDEX, (Vector2){GetRigidbody(PLAYER_INDEX).velocity.x, 0});
+            
+            // Add jumping force in Y axis
+            AddRigidbodyForce(PLAYER_INDEX, (Vector2){0, jumpForce});
+        }
+        
+        // Check movement buttons input
+        if(IsKeyDown(KEY_RIGHT) || IsKeyDown(KEY_D))
+        {
+            // Set rigidbody velocity in X based on moveSpeed value and apply the same Y velocity that it already has
+            SetRigidbodyVelocity(PLAYER_INDEX, (Vector2){moveSpeed, GetRigidbody(PLAYER_INDEX).velocity.y});
+        }
+        else if(IsKeyDown(KEY_LEFT) || IsKeyDown(KEY_A))
+        {
+            // Set rigidbody velocity in X based on moveSpeed negative value and apply the same Y velocity that it already has
+            SetRigidbodyVelocity(PLAYER_INDEX, (Vector2){-moveSpeed, GetRigidbody(PLAYER_INDEX).velocity.y});
+        }
+        
+        // Check debug mode toggle button input
+        if(IsKeyPressed(KEY_P))
+        {
+            // Update program physics value
+            worldPhysics.debug = !worldPhysics.debug;
+            
+            // Update internal physics value
+            SetPhysics(worldPhysics);
+        }
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+            
+            // Draw information
+            DrawText("Use LEFT / RIGHT to MOVE and SPACE to JUMP", (screenWidth - MeasureText("Use LEFT / RIGHT to MOVE and SPACE to JUMP", 20)) / 2, screenHeight * 0.20f, 20, LIGHTGRAY);
+            DrawText("Use P to switch DEBUG MODE", (screenWidth - MeasureText("Use P to switch DEBUG MODE", 20)) / 2, screenHeight * 0.3f, 20, LIGHTGRAY);
+            
+            // Check if debug mode is enabled
+            if(worldPhysics.debug)
+            {
+                // Draw every internal physics stored collider if it is active
+                for(int i = 0; i < 2; i++)
+                {
+                    if(GetCollider(i).enabled)
+                    {
+                        DrawRectangleLines(GetCollider(i).bounds.x, GetCollider(i).bounds.y, GetCollider(i).bounds.width, GetCollider(i).bounds.height, GREEN);
+                    }
+                }
+                
+            }
+            else
+            {
+                // Draw player
+                DrawRectangleRec((Rectangle){player.position.x, player.position.y, player.scale.x, player.scale.y}, GRAY);
+                
+                // Draw floor
+                DrawRectangleRec((Rectangle){floor.position.x, floor.position.y, floor.scale.x, floor.scale.y}, BLACK);
+            }
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------   
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}