raylib-src/examples/physac/physics_friction.c

/*******************************************************************************************
*
*   Physac - Physics friction
*
*   NOTE 1: Physac requires multi-threading, when InitPhysics() a second thread is created to manage physics calculations.
*   NOTE 2: Physac requires static C library linkage to avoid dependency on MinGW DLL (-static -lpthread)
*
*   Use the following line to compile:
*
*   gcc -o $(NAME_PART).exe $(FILE_NAME) -s -static  /
*       -lraylib -lpthread -lglfw3 -lopengl32 -lgdi32 -lopenal32 -lwinmm /
*       -std=c99 -Wl,--subsystem,windows -Wl,-allow-multiple-definition
*   
*   Copyright (c) 2016-2018 Victor Fisac
*
********************************************************************************************/

#include "raylib.h"

#define PHYSAC_IMPLEMENTATION
#define PHYSAC_NO_THREADS
#include "physac.h"

int main()
{
    // Initialization
    //--------------------------------------------------------------------------------------
    int screenWidth = 800;
    int screenHeight = 450;

    SetConfigFlags(FLAG_MSAA_4X_HINT);
    InitWindow(screenWidth, screenHeight, "Physac [raylib] - Physics friction");

    // Physac logo drawing position
    int logoX = screenWidth - MeasureText("Physac", 30) - 10;
    int logoY = 15;

    // Initialize physics and default physics bodies
    InitPhysics();

    // Create floor rectangle physics body
    PhysicsBody floor = CreatePhysicsBodyRectangle((Vector2){ screenWidth/2, screenHeight }, screenWidth, 100, 10);
    floor->enabled = false; // Disable body state to convert it to static (no dynamics, but collisions)
    PhysicsBody wall = CreatePhysicsBodyRectangle((Vector2){ screenWidth/2, screenHeight*0.8f }, 10, 80, 10);
    wall->enabled = false; // Disable body state to convert it to static (no dynamics, but collisions)

    // Create left ramp physics body
    PhysicsBody rectLeft = CreatePhysicsBodyRectangle((Vector2){ 25, screenHeight - 5 }, 250, 250, 10);
    rectLeft->enabled = false; // Disable body state to convert it to static (no dynamics, but collisions)
    SetPhysicsBodyRotation(rectLeft, 30*DEG2RAD);

    // Create right ramp  physics body
    PhysicsBody rectRight = CreatePhysicsBodyRectangle((Vector2){ screenWidth - 25, screenHeight - 5 }, 250, 250, 10);
    rectRight->enabled = false; // Disable body state to convert it to static (no dynamics, but collisions)
    SetPhysicsBodyRotation(rectRight, 330*DEG2RAD);

    // Create dynamic physics bodies
    PhysicsBody bodyA = CreatePhysicsBodyRectangle((Vector2){ 35, screenHeight*0.6f }, 40, 40, 10);
    bodyA->staticFriction = 0.1f;
    bodyA->dynamicFriction = 0.1f;
    SetPhysicsBodyRotation(bodyA, 30*DEG2RAD);

    PhysicsBody bodyB = CreatePhysicsBodyRectangle((Vector2){ screenWidth - 35, screenHeight*0.6f }, 40, 40, 10);
    bodyB->staticFriction = 1;
    bodyB->dynamicFriction = 1;
    SetPhysicsBodyRotation(bodyB, 330*DEG2RAD);

    SetTargetFPS(60);
    //--------------------------------------------------------------------------------------

    // Main game loop
    while (!WindowShouldClose())    // Detect window close button or ESC key
    {
        // Update
        //----------------------------------------------------------------------------------
        RunPhysicsStep();

        if (IsKeyPressed('R'))    // Reset physics input
        {
            // Reset dynamic physics bodies position, velocity and rotation
            bodyA->position = (Vector2){ 35, screenHeight*0.6f };
            bodyA->velocity = (Vector2){ 0, 0 };
            bodyA->angularVelocity = 0;
            SetPhysicsBodyRotation(bodyA, 30*DEG2RAD);
            
            bodyB->position = (Vector2){ screenWidth - 35, screenHeight*0.6f };
            bodyB->velocity = (Vector2){ 0, 0 };
            bodyB->angularVelocity = 0;
            SetPhysicsBodyRotation(bodyB, 330*DEG2RAD);
        }
        //----------------------------------------------------------------------------------

        // Draw
        //----------------------------------------------------------------------------------
        BeginDrawing();

            ClearBackground(BLACK);

            DrawFPS(screenWidth - 90, screenHeight - 30);

            // Draw created physics bodies
            int bodiesCount = GetPhysicsBodiesCount();
            for (int i = 0; i < bodiesCount; i++)
            {
                PhysicsBody body = GetPhysicsBody(i);

                if (body != NULL)
                {
                    int vertexCount = GetPhysicsShapeVerticesCount(i);
                    for (int j = 0; j < vertexCount; j++)
                    {
                        // Get physics bodies shape vertices to draw lines
                        // Note: GetPhysicsShapeVertex() already calculates rotation transformations
                        Vector2 vertexA = GetPhysicsShapeVertex(body, j);

                        int jj = (((j + 1) < vertexCount) ? (j + 1) : 0);   // Get next vertex or first to close the shape
                        Vector2 vertexB = GetPhysicsShapeVertex(body, jj);

                        DrawLineV(vertexA, vertexB, GREEN);     // Draw a line between two vertex positions
                    }
                }
            }

            DrawRectangle(0, screenHeight - 49, screenWidth, 49, BLACK);

            DrawText("Friction amount", (screenWidth - MeasureText("Friction amount", 30))/2, 75, 30, WHITE);
            DrawText("0.1", bodyA->position.x - MeasureText("0.1", 20)/2, bodyA->position.y - 7, 20, WHITE);
            DrawText("1", bodyB->position.x - MeasureText("1", 20)/2, bodyB->position.y - 7, 20, WHITE);

            DrawText("Press 'R' to reset example", 10, 10, 10, WHITE);

            DrawText("Physac", logoX, logoY, 30, WHITE);
            DrawText("Powered by", logoX + 50, logoY - 7, 10, WHITE);

        EndDrawing();
        //----------------------------------------------------------------------------------
    }

    // De-Initialization
    //--------------------------------------------------------------------------------------   
    ClosePhysics();       // Unitialize physics
    
    CloseWindow();        // Close window and OpenGL context
    //--------------------------------------------------------------------------------------

    return 0;
}