Using SpriteBatch.Begin() within other SpriteBatch.Begin()

Question

Hey guys, i'm trying to use the following drawing logic:

Class Game
{
    Character x;

    public Draw(...)
    {
        spriteBatch.Begin(transformation1);
        x.Draw();
        spriteBatch.End();

        spriteBatch.Begin(transformation2);
        otherThing.Draw();
        spriteBatch.End();
    }
}

Class Character
{
    Animation[] animations;
    int currentAnimation;

    public Draw(...)
    {
        this.animations[this.currentAnimation].Draw();
    }
}

Class Animation
{
    Frame[] frames;
    int currentFrame;

    public Draw(...)
    {
        this.frames[this.currentFrame].Draw();
    }
}
Class Frame
{
    Texture2D texture;
    Texture2D shadow;

    public Draw(...)
    {
        spriteBatch.Begin(sub_transformation1);
        spriteBatch.Draw(texture1, ...);
        spriteBatch.End();

        spriteBatch.Begin(sub_transformation2);
        spriteBatch.Draw(shadow, ...);
        spriteBatch.End();
    }
}

If i try this logic i get a "Begin cannot be called again until End has been successfully called." error. So i'm asking if this logic is possible / makes sense? I'm using Begin() within Begin() to make additive transformations. If i have a character on x = 100 and y = 100 and i want the texture and shadow of the frame and everything else i want (bounding boxes, etc), to be drawn using that 100,100 translation, plus the -Xscale or +Xscale to flip horizontally the character (i know i could use the SpriteEffects.FlipHorizontally in the .Draw, but i wanted something that applied automatically to the bottom levels (animation and frame)), and finally in the Frame level the texture has a transformation on top of the one from the character and the shadow has another one. Don't know if i explained myself well, but ask if you have any doubts.

Thanks a lot.

score 2 · Accepted Answer · edited Apr 13 '17 at 12:18

I kind of understand where you're coming from, but it just isn't possible. SpriteBatch can't be hierarchical like you're wanting. Your objects, however, can.

Edited slightly to address your question below:

Class Frame
{
    // World - parent transformation to build from, passed 
    // from animation, from character, on up the chain...
    // localTransform - local coordinates
    // shadowTransform - maybe not needed?
    public Draw(Matrix world, Matrix localTransform, Matrix shadowTransform)
    {
        spriteBatch.Begin();
        spriteBatch.Draw(
            texture1, 
            ..., 
            Matrix.Transform(world * localTransform),
            ...);

        spriteBatch.Draw(
            shadowTexture, 
            ..., 
            Matrix.Transform(world * localTransform * shadowTransform), 
            ...);

        spriteBatch.End();
    }
}

You don't have to pass down all the character or object information into the frame - just need a transform to be set by the frame parent. Your original code was already receiving a transform (sub_transformation1 and 2) from somewhere - here we just pass that value into the Draw function. You could make the localTransform a class variable too, set it on instantiation.

The Animation class would have a similar Draw(Matrix world...) signature. I think it achieves what you're looking for and kind of similar to how OpenGL handles things - just more manual (from the little I remember of it from years ago).

Side note, there is gamedev.stackexchange.com for game related questions too.

That makes sense, but that would imply that Animation and Frame were passed down with the Position, Facing direction, etc from the Character. I want something more independent and generic so that i could use them with upper classes that apply transformations besides Character. I come from a OpenGL / DirectX background, so not being able to do these simple things kinda confuses me. I know that XNA has a more DirectX way of doing things using CreateOrthoMatrix and using DrawPrimitives, although that's a lot more work than using SpriteBatch, but it looks like i have to use that to do what i want. — xlar8or, Mar 16 '11 at 11:20

score 0 · Answer 2 · answered Mar 15 '11 at 02:39

If you think about SpriteBatch in terms of the traditional World/View/Project model of transformation:

You should be doing your "World" transformation in the Draw call. That is to say, if your sprite is at position you should draw it at position. If it has a shadow at position + 100, draw it there as well.

You should be doing your View (and Project if you're getting fancy) transformation - that is your "camera" transformation - in the Begin call.

(There are a few situations where you can only get the world transform you want with a matrix, but that is quite unusual.)

You cannot "stack" transformations with SpriteBatch, you'd have to implement such a thing externally.

Using SpriteBatch.Begin() within other SpriteBatch.Begin()

2 Answers2