SSAA (Screen Space Anti-Aliasing) and bonus: NFAA
Posted: Thu Nov 18, 2010 4:00 am
One of these days I found this technique that the author calls SSAA: http://gamestart3d.com/blog/ssaa-antialiasing and which, in turn, is based on an idea called NFAA: http://www.gamedev.net/community/forums ... _id=580517 . So basically what I did to get started learning a bit about the compositor system was to implement both of them as OGRE compositors (and also converted the SSAA shader to cg, which was pretty easy).
About the usefulness of both of them, just remember that they can be used in some places that "conventional" AA can't, especially deferred shading
The SSAA one is a bit faster for me and personally I think it looks better as well but that might just be due to bad parameter adjustments.
In any case, here are the screenshots, in order: without AA, SSAA and NFAA.
Also, a close-up comparison of the barrel with SSAA:
And now, the code for the SSAA compositor & material, pretty straightforward stuff (actually I copied most of it from the Tiling compositor
). They're identical for NFAA, just change the fragment program entry point.
And now the shaders code.
About the usefulness of both of them, just remember that they can be used in some places that "conventional" AA can't, especially deferred shading
The SSAA one is a bit faster for me and personally I think it looks better as well but that might just be due to bad parameter adjustments.
In any case, here are the screenshots, in order: without AA, SSAA and NFAA.
Also, a close-up comparison of the barrel with SSAA:
And now, the code for the SSAA compositor & material, pretty straightforward stuff (actually I copied most of it from the Tiling compositor
). They're identical for NFAA, just change the fragment program entry point.Code: Select all
compositor SSAA
{
technique
{
texture rt0 target_width target_height PF_A8R8G8B8
target rt0
{
input previous
}
target_output
{
input none
pass render_quad
{
material Ogre/Compositor/SSAA
input 0 rt0
}
}
}
}Code: Select all
fragment_program Ogre/Compositor/SSAA_FP cg
{
source SSAA_FP.cg
entry_point SSAA_ps
profiles ps_2_0 arbfp1
}
material Ogre/Compositor/SSAA
{
technique
{
pass
{
cull_hardware none
cull_software none
depth_func always_pass
vertex_program_ref Ogre/Compositor/StdQuad_Tex2a_vp
{
}
fragment_program_ref Ogre/Compositor/SSAA_FP
{
param_named_auto ScreenSize inverse_texture_size 0
}
texture_unit source
{
tex_coord_set 0
tex_address_mode clamp
filtering trilinear
}
}
}
}Code: Select all
float lumRGB(float3 v)
{
return dot(v, float3(0.212, 0.716, 0.072));
}
float4 SSAA_ps(float2 UV : TEXCOORD0,
uniform float4 ScreenSize,
sampler source : register(s0)) : COLOR
{
float2 inverse_buffer_size = ScreenSize.xy;
float w = 1.75;
float t = lumRGB(tex2D(source, UV + float2(0.0, -1.0) * w * inverse_buffer_size).xyz),
l = lumRGB(tex2D(source, UV + float2(-1.0, 0.0) * w * inverse_buffer_size).xyz),
r = lumRGB(tex2D(source, UV + float2(1.0, 0.0) * w * inverse_buffer_size).xyz),
b = lumRGB(tex2D(source, UV + float2(0.0, 1.0) * w * inverse_buffer_size).xyz);
vec2 n = vec2(-(t - b), r - l);
float nl = length(n);
if (nl < (1.0 / 16.0))
return tex2D(source, UV);
else
{
n *= inverse_buffer_size / nl;
float4 o = tex2D(source, UV),
t0 = tex2D(source, UV + n * 0.5) * 0.9,
t1 = tex2D(source, UV - n * 0.5) * 0.9,
t2 = tex2D(source, UV + n) * 0.75,
t3 = tex2D(source, UV - n) * 0.75;
return (o + t0 + t1 + t2 + t3) / 4.3;
}
}
float4 NFAA_ps(float2 UV : TEXCOORD0,
uniform float4 ScreenSize,
sampler source : register(s0)) : COLOR
{
float2 vPixelViewport = ScreenSize.xy;
const float fScale = 1.75;
// Offset coordinates
float2 upOffset = float2( 0, vPixelViewport.y )* fScale;
float2 rightOffset = float2( vPixelViewport.x, 0 ) * fScale;
float topHeight = lumRGB( tex2D( source, UV.xy + upOffset).rgb );
float bottomHeight = lumRGB( tex2D( source, UV.xy - upOffset).rgb );
float rightHeight = lumRGB( tex2D( source, UV.xy + rightOffset).rgb );
float leftHeight = lumRGB( tex2D( source, UV.xy - rightOffset).rgb );
float leftTopHeight = lumRGB( tex2D( source, UV.xy - rightOffset + upOffset).rgb );
float leftBottomHeight = lumRGB( tex2D( source, UV.xy - rightOffset - upOffset).rgb );
float rightBottomHeight = lumRGB( tex2D( source, UV.xy + rightOffset + upOffset).rgb );
float rightTopHeight = lumRGB( tex2D( source, UV.xy + rightOffset - upOffset).rgb );
// Normal map creation
float sum0 = rightTopHeight + topHeight + rightBottomHeight;
float sum1 = leftTopHeight + bottomHeight + leftBottomHeight;
float sum2 = leftTopHeight + leftHeight + rightTopHeight;
float sum3 = leftBottomHeight + rightHeight + rightBottomHeight;
float vec1 = (sum1 - sum0);
float vec2 = (sum2 - sum3);
// Put them together and scale.
float2 Normal = float2( vec1, vec2) * vPixelViewport * fScale;
// Color
float4 Scene0 = tex2D( source, UV.xy );
float4 Scene1 = tex2D( source, UV.xy + Normal.xy );
float4 Scene2 = tex2D( source, UV.xy - Normal.xy );
float4 Scene3 = tex2D( source, UV.xy + float2(Normal.x, -Normal.y) * 0.5 );
float4 Scene4 = tex2D( source, UV.xy - float2(Normal.x, -Normal.y) * 0.5 );
// Final color
return (Scene0 + Scene1 + Scene2 + Scene3 + Scene4) * 0.2;
}