"Lighting" specific objects

1

I have done something similar to this:

1

2

My question is, what would I have to do to draw that lighting effect only on the pillar and not the background ? Is there something like ignoring certain sprites (background) when using BlendState.Additive ? How would that work ? Here is how i’m drawing it now.

//draw background
spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.Opaque);
spriteBatch.Draw(Background, Vector2.Zero, Color.White);
spriteBatch.End();

//draw pillar
spriteBatch.Begin(SpriteSortMode.Deferred);
spriteBatch.Draw(Texture, new Rectangle(PillarX, PillarY, Width, Height), Color.White);
spriteBatch.End();

//draw lighting sprite in additive mode
spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.Additive);
spriteBatch.Draw(LightTexture, pos, null, Color.OrangeRed, 0f, Vector2.Zero, 
    scale, SpriteEffects.None, 0f);
spriteBatch.End();
2

You can use the stencil buffer to mask objects. When you google “xna stencil buffer example”, you should be able to find several examples.

3

Since your light effect appears to be a sprite, the easiest way to go is to specify a source rectangle in the last draw. A source rectangle specifies which area of a sprite should be drawn on the screen. For example you can draw the top left corner of your sprite by using a rectangle of (0, 0, width/2, height/2).
You have to calculate the source rectangle yourself so it will only draw in the right area of the screen.

4

that would be impossible to do in any other shape than rectangle though. the question is just an example of what i am trying to do. not all of it

5

The problem with this is that the object is not just a pillar. it is also a 3D model too. Will i be able to use stencil buffer for it ?

6

If it’s a 3D model then you should use proper light effect and that works on model level (draw this model with the light effect, draw other model with other effect).

7

i am making a breakout game with 3D models as cubes and my ball is supposed to shine my 3D cubes when it is close to the cubes as a result of drawing the sprite i have in my question

8

Yes, the stencil buffer works for 2D and 3D.