[solved] multiply two outputs, 2D + 3D render to texture

[milkshakeman]

Hi,

I have the following situation:
- an isometric world, created with draw2DImage, oldskool bitblitting a map together from diamond shaped isometric sprites.
- Every tile has its own 3D shape, all shapes together form a low poly 3D map, which is not rendered but just used for line of fire checking.

Now I want to try something crazy, I know in theory it should work, but I can not find the right way to do it in Irrlicht, if even possible.


Lets say I have a house in my isometric game, drawn with draw2DImage:


Suppose I put a light in my normally invisible line-of-fire checking 3D world and render it out I may have something like this: (everything is in plain white texture)


The only thing I would have to do is multiply both outputs to have this endresult:


edit:

I got the idea from here:
http://www.gamedev.net/community/forums ... _id=447054

[milkshakeman]

Allright, I found render draw2DImage to a texture works exactly the same as 3D rendering to texture I was making it more complicated than it was I guess...

So now I have them both in a texture, the only trick now is to multiply the two textures... I'm looking into shaders...

[Lonesome Ducky]

Yes, shaders are definitely your best bet. You could add a blending mode in the irrlicht driver itself, but you'd have to modify a lot more code than just writing a shader.

[milkshakeman]

I got it the technique working now, hehe.

So what I do is, create a node, with two materials assigned to two render targets, and the materialtype set to my shader:

Code: Select all

		rt1 = driver->addRenderTargetTexture(core::dimension2d<u32>(256,256), "RTT1");
		rt2 = driver->addRenderTargetTexture(core::dimension2d<u32>(256,256), "RTT2");
		
		test->setMaterialTexture(0, rt1); // set material of node to render target
		test->setMaterialTexture(1, rt2); // set material of node to render target
		test->setMaterialType((video::E_MATERIAL_TYPE)newMaterialType1);

In the drawing loop I set the first rendertarget and draw 2D stuff, then I set the second rendertarget active and draw the 3D stuff,
then I set back to rendertarget 0 and draw the result.

The shader I used is this one:

Code: Select all

sampler2D   tex0: register(s0);
sampler2D   tex1: register(s1);

struct PS_INPUT 
{ 
   float2 TexCoord : TEXCOORD0; 
}; 

float4 pixelMain(PS_INPUT Input) : COLOR0 
{    
   float4 col0 = tex2D(tex0, Input.TexCoord); 
   float4 col1 = tex2D(tex1, Input.TexCoord); 

   float4 final = col0*col1; 

   return final; 
} 

[slavik262]

If you're just multiplying by a fully white texture, you really don't even need it. You can just sample the other texture.

[Lonesome Ducky]

If you're just multiplying by a fully white texture, you really don't even need it. You can just sample the other texture.

I think he's multiplying the house texture with the shadow texture.

[milkshakeman]

If you're just multiplying by a fully white texture, you really don't even need it. You can just sample the other texture.

I think he's multiplying the house texture with the shadow texture.

Yes that is what I'm doing.
So the white parts result in the original colors, and black results in black.

[slavik262]

I stand corrected.

Nicely done.

[milkshakeman]

And I want to give proper credits to the people that deserve it, because for the concept itself I was inspired by O-san from gamedev.net.
See this thread:
http://www.gamedev.net/community/forums ... _id=447054

[Mel]

You don't even need a shader for that. Use the material type EMT_LIGHTMAP, and it should be the same :)But it is a nice practice to start learning shaders.

[Lonesome Ducky]

You don't even need a shader for that. Use the material type EMT_LIGHTMAP, and it should be the same :)But it is a nice practice to start learning shaders.

That requires a second set of texture coordinates doesn't it? I'm sure it could still work, but the shader will be much more reusable as you won't have to convert vertex types.

[hybrid]

At least for OpenGL, the first texture coord is used if no second is available but requested. Not sure if I fixed that for d3d as well. But it ought be.

[Mel]

Yes, it is needed the second set of UV coordinates, i forgot it, at least, in DX it is needed. Well, in any case, it would be easy, you just need to copy the first set into the second. But using the shaders is simpler, indeed.