raylib/docs/examples/web/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 $(RAYLIB_DIR)\raylib\raylib_icon -static -lraylib -lpthread 
*   -lglfw3 -lopengl32 -lgdi32 -lopenal32 -lwinmm -std=c99 -Wl,--subsystem,windows -Wl,-allow-multiple-definition
*   
*   Copyright (c) 2017 Victor Fisac
*
********************************************************************************************/

#include "raylib.h"

#define PHYSAC_IMPLEMENTATION
#include "physac.h"

#if defined(PLATFORM_WEB)
    #include <emscripten/emscripten.h>
#endif

//----------------------------------------------------------------------------------
// Global Variables Definition
//----------------------------------------------------------------------------------
int screenWidth = 800;
int screenHeight = 450;

// Physac logo drawing position
int logoX = 0;
int logoY = 15;

PhysicsBody bodyA;
PhysicsBody bodyB;

//----------------------------------------------------------------------------------
// Module Functions Declaration
//----------------------------------------------------------------------------------
void UpdateDrawFrame(void);     // Update and Draw one frame

//----------------------------------------------------------------------------------
// Main Enry Point
//----------------------------------------------------------------------------------
int main()
{
    // Initialization
    //--------------------------------------------------------------------------------------
    SetConfigFlags(FLAG_MSAA_4X_HINT);
    InitWindow(screenWidth, screenHeight, "Physac [raylib] - Physics friction");

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

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

    // Create floor rectangle physics body
    PhysicsBody ground = CreatePhysicsBodyRectangle((Vector2){ screenWidth/2, screenHeight }, screenWidth, 100, 10);
    ground->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
    bodyA = CreatePhysicsBodyRectangle((Vector2){ 35, screenHeight*0.6f }, 40, 40, 10);
    bodyA->staticFriction = 0.1f;
    bodyA->dynamicFriction = 0.1f;
    SetPhysicsBodyRotation(bodyA, 30*DEG2RAD);

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

#if defined(PLATFORM_WEB)
    emscripten_set_main_loop(UpdateDrawFrame, 0, 1);
#else
    SetTargetFPS(60);   // Set our game to run at 60 frames-per-second
    //--------------------------------------------------------------------------------------
    
    // Main game loop
    while (!WindowShouldClose())    // Detect window close button or ESC key
    {
        UpdateDrawFrame();
    }
#endif

    // De-Initialization
    //--------------------------------------------------------------------------------------   
    ClosePhysics();       // Uninitialize physics

    CloseWindow();        // Close window and OpenGL context
    //--------------------------------------------------------------------------------------

    return 0;
}

//----------------------------------------------------------------------------------
// Module Functions Definition
//----------------------------------------------------------------------------------
void UpdateDrawFrame(void)
{
    // Update
    //----------------------------------------------------------------------------------
    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();
    //----------------------------------------------------------------------------------
}