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global renderImage as integer
global renderObj as integer

LoadShader( 5, "Quad.vs", "Bloom.ps" ) // combines image 5 and 2 into the final output

renderImage = CreateRenderImage(512,512,0,0)

RenderObj = CreateObjectQuad()

Update(0)
	
	SetRenderToImage( renderimage,0 ) // render into image 2, using an internal depth buffer
	ClearScreen()
	Render() // draw the scene as normal
	SetRenderToScreen()
	SetObjectImage(renderObj,renderImage,0)
	SetObjectShader( renderObj, 5 ) // apply the bloom shader to the quad, this will do the work of blending image 5 and image 2
	render()
	Swap()

uniform sampler2D texture0; // the texture with the scene you want to blur
varying vec2 posVarying;
varying vec2 uvVarying;

uniform vec2 BlurSize;

void main()
{
    vec4 sum = vec4(0.0);
    for (float x = -4.0; x <= 4.0; x++)
        for (float y = -4.0; y <= 4.0; y++)
            sum += texture2D(texture0,vec2(uvVarying.x + x * BlurSize.x, uvVarying.y + y * BlurSize.y)) / 81.0;
			
    gl_FragColor = sum;
}

// create some intermediate images for the full screen shader
CreateRenderImage( 2, 1024, 1024, 0, 0 ) // initial render
CreateRenderImage( 3, 512, 512, 0, 0 ) // reduction 1
CreateRenderImage( 4, 256, 256, 0, 0 ) // reduction 2
CreateRenderImage( 5, 128, 128, 0, 0 ) // reduction 3
CreateRenderImage( 6, 128, 128, 0, 0 ) // blur 1
// we then blur a second time with image 5 as the output, as it is the right size and we don't need it anymore
// image 5 (blurry) is then blended with image 2 (sharp) to produce the final output shown on the screen

// load the shaders for each stage, Quad.vs does a simply vertex transformation to make the 3D plane perfectly fit the entire screen
LoadShader( 1, "Quad.vs", "Initial.ps" )
LoadShader( 2, "Quad.vs", "Reduction.ps" ) // same shader for all three reduction steps
LoadShader( 3, "Quad.vs", "Blur1.ps" )
LoadShader( 4, "Quad.vs", "Blur2.ps" )
LoadShader( 5, "Quad.vs", "Bloom.ps" ) // combines image 5 and 2 into the final output

// make a plane to display images to the screen so they can be modified by shaders.
// planes used for this purpose are generally called quads, AGK has a special Quad primitive
// that means it can trake some shortcuts in the rendering pipeline, Quads will never be
// rendered to the screen unless you specifically draw it with DrawObject()
CreateObjectQuad( 8 )

    // update the scene, this should only be called once
    Update(0)

    // full screen bloom process
    // first Render() as normal to image 2
    SetRenderToImage( 2, -1 ) // render into image 2, using an internal depth buffer
	ClearScreen() // make sure the image is clean
	Render() // draw the scene as normal

    // do some post processing on our newly rendered image 2
    SetObjectImage( 8, 2, 0 ) // apply image 2 to the quad
	SetObjectShader( 8, 1 ) // set our first shader to the quad, this does some processing on the image to make it suitable for bloom
	SetRenderToImage( 3, 0 ) // we will output to image 3 which is half the size, so this is also a reduction whilst shader 1 does some processing
	ClearScreen() // clean image 3
	DrawObject( 8 ) // draw the quad and nothing else, this makes it nice and fast

    // take our newly rendered image 3 and reduce it further
	SetObjectImage( 8, 3, 0 ) // apply image 3 to the quad, this removes image 2 which will remain unchanged from now on
	SetObjectShader( 8, 2 ) // set the reduction shader which does nothing but reduce the image size
	SetRenderToImage( 4, 0 ) // output to image 4 which is half the size of image 3
	ClearScreen() // clean image 4
	DrawObject( 8 ) // draw the quad and nothing else

    // take our newly rendered image 4 and reduce it further
	SetObjectImage( 8, 4, 0 ) // apply image 4 to the quad
	SetObjectShader( 8, 2 ) // added for clarity, the quad is already using shader 2
	SetRenderToImage( 5, 0 ) // output to image 5 which is half the size of image 4
	ClearScreen() // clean image 5
	DrawObject( 8 ) // draw the quad and nothing else

    // we now have a low quality 128x128 copy of our scene in image 5, lets blur this so it creates a nice bloom effect

	SetObjectImage( 8, 5, 0 ) // apply image 5 to the quad
	SetObjectShader( 8, 3 ) // set the first blur shader, this does a horizontal blur across the pixels
	SetRenderToImage( 6, 0 ) // output to image 6, which is the same size as image 5
	ClearScreen() // clean image 6
	DrawObject( 8 ) // draw the quad and nothing else

	SetObjectImage( 8, 6, 0 ) // apply image 6 to the quad
	SetObjectShader( 8, 4 ) // set the second blur shader, this does a vertical blur across the pixels to finish the blur effect
	SetRenderToImage( 5, 0 ) // output to image 5 as it is no longer being used and is the right size for this step
	ClearScreen() // clean image 5
	DrawObject( 8 ) // draw the quad and nothing else

	// we now have a very blurry image 5 and a nice sharp image 2 from the very beginning (plus some intermediate
    // images 3,4,6 that we don't need anymore), we can combine image 5 and 2 to create a nice bloom effect

    SetObjectImage( 8, 2, 0 ) // set image 2 to texture stage 0 on the quad
	SetObjectImage( 8, 5, 1 ) // set image 2 to texture stage 1 on the quad
	SetObjectShader( 8, 5 ) // apply the bloom shader to the quad, this will do the work of blending image 5 and image 2
	SetRenderToScreen() // send this output to the screen, this is the only thing the user will see from the entire process
	DrawObject( 8 ) // draw the qaud and nothing else, remember image 2 already contains our original scene so we don't need to draw that again

    // don't use Sync() here as it will redraw the entire scene again, we have already drawn the scene and post processed it
    Swap()