Cool Stuff

Emerging Capabilities• Image Processing• Massively Multipass

Image Processing• Scene Post-Processing

– Light Blooms– Depth of field– Posterization

• Traditional Stuff– Convolution Filters– Frequency Space Operations

Convolutions• Filter Mask Application

– Implemented by shaders– Spill Intermediates to Float Buffers– Sped up by Using Separable Filters

Fourier Transform• Transformation from image space

to frequency space– Allows complex filtering

• Large convolutions• Frequency limiting filters

– Band limit– Band Pass– Band Stop

Fourier Transform by GPU• Multipass algorithm• Uses floating point textures• Uses floating point destinations• Real-time on 512x512

Fourier Transform Cnt’d• Decimation in time algorithm• Requires

– Log2(width) + log2(height) + 2 passes

Fourier Passes• Horizontal scramble

– Rearrange pixels in rows• Log2(width) horizontal butterflies

– Complex multiply accumulates• Vertical scramble

– Rearrange pixels in columns• Log2(height) vertical butterflies

– Complex multiply accumulates

Massive Multipass• Implement Complex Algorithms

– Apply Shaders to Temporary Float Buffers

– Prelude to the Future• High-level Shading Languages• F-Buffers

Questions?• ehart@ati.com