How can I detect transparent areas in a sprite in Unity-CodePudding

I have a 1024x1024 pixel sprite with some transparent areas in it. I am rendering it on a game scene using Sprite Renderer. Is there any way check whether the pixel at mouse position is transparent or not when the mouse is hovered over it.

CodePudding user response：

We could cast ray and get the world position of our hit point, Here I am assuming your SpriteRenderer has a collider.

private RaycastHit CastRay()
{
    RaycastHit hit;
    Ray ray = _camera.ScreenPointToRay(Input.mousePosition);
    Physics.Raycast(ray, out hit);
    return hit;
}

Then we need a method to convert that world space into texture coordinates

public Vector2 TextureSpaceCoord(Vector3 worldPos) {
    float ppu = _sprite.pixelsPerUnit;

    Vector2 localPos = transform.InverseTransformPoint(worldPos) * ppu;

    var texSpacePivot = new Vector2(_sprite.rect.x, _sprite.rect.y)   _sprite.pivot;
    Vector2 texSpaceCoord = texSpacePivot   localPos;

    return texSpaceCoord;
}

Once we get the texture coordinates we could just use GetPixel() of Texture2D to get the color

private void PickColor()
{
    RaycastHit hit = CastRay();
    if (hit.collider != null)
    {
        Vector2 coord = TextureSpaceCoord(hit.point);
        Color selectedColor = _sprite.texture.GetPixel((int) coord.x, (int) coord.y);

        // Here you can check if color is transparent
        if(selectedColor == Color.clear){
            // do stuff
        }
    }
}

You could call the PickColor() in Update(), _camera would be Camera.main and _sprite would be the Sprite of your SpriteRenderer