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i am new to raylib and wanted to make a little 2d ball thing, and i don't know how to stop the sprite from going of the screen, it only works with 2 edges and not the others, would anybody please help?

My C++ file: game.cpp:

#include <raylib.h>

int main() {

    InitWindow(800, 600, "My Game!");

    // Vector2 ballPosition = {400.0f, 300.0f};
    Vector2 ballPosition = { (float)800/2, (float)600/2 };

    SetTargetFPS(60);

    while(!WindowShouldClose()) {

        if (IsKeyDown(KEY_RIGHT)) ballPosition.x += 2.0f;
        if (IsKeyDown(KEY_LEFT)) ballPosition.x -= 2.0f;
        if (IsKeyDown(KEY_UP)) ballPosition.y -= 2.0f;
        if (IsKeyDown(KEY_DOWN)) ballPosition.y += 2.0f;

        DrawText("move the ball with arrow keys", 10, 10, 20, DARKGRAY);

        Texture2D ball = LoadTexture("ball.png");

        DrawTexture(ball, ballPosition.x - 50, ballPosition.y - 50, WHITE);

        if (ballPosition.x < 0) ballPosition.x = 0;
        if (ballPosition.x > 800) ballPosition.x = 800;
        if (ballPosition.y < 0) ballPosition.y = 0;
        if (ballPosition.y > 600) ballPosition.y = 600;

        BeginDrawing();
        ClearBackground(RAYWHITE);
        
        // Vector2 mousePosition = GetMousePosition();
        // ballPosition = mousePosition;
        // DrawCircleV(ballPosition, 20.0f, BLUE);
        
        EndDrawing();
    }

    CloseWindow();

    return 0;
}
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Ralph Turner
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  • Unrelated but `Texture2D ball = LoadTexture("ball.png");` should probably be outside of the loop, there is no point in loading that image every single frame. Also can you specify which 2 edges it does work with? (I'm assiming the < 0 but who knows) – Borgleader Jun 29 '22 at 21:53
  • I moved the ```Texture2D ball = LoadTexture("ball.png");``` outside of the loop but it seems to have done nothing. – Ralph Turner Jun 29 '22 at 22:00
  • I know thats why I said it was unrelated, its not the source of your problem but its an optimization, theres no point in loading the same image every frame. – Borgleader Jun 29 '22 at 22:10

1 Answers1

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Took me a while but your problem is a combination of the offset for drawing the ball texture and how you check for the bounds of the screen (assuming the image is a 50x50, you didn't specify).

enter image description here

Notice I've locally added a circle directly at the ballposition (right after the DrawTextureCall):

DrawCircleV(ballPosition, 2.0f, MAROON);

Since this is to the right and bottom of the image, your bounds check will only be correct for the right and bottom edges. For the left and top edges the entire image disappears before the ballposition hits the edge.

In my opinion you should draw the image at the ballposition and adjust the bounds check to take the image size into account:

    const float ballHalfSize = ball.width / 2.0f; // assuming square image
    DrawTexture(ball, int(ballPosition.x - ballHalfSize), int(ballPosition.y - ballHalfSize), WHITE);

    if ((ballPosition.x - ballHalfSize) < 0) ballPosition.x = ballHalfSize;
    if ((ballPosition.x + ballHalfSize) > 800) ballPosition.x = 800 - ballHalfSize;
    if ((ballPosition.y - ballHalfSize) < 0) ballPosition.y = ballHalfSize;
    if ((ballPosition.y + ballHalfSize) > 600) ballPosition.y = 600 - ballHalfSize;

With this new version I get correct collision behavior on all 4 edges of the screen.

Borgleader
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