How to get reach within shader better five key tips explained

Accurately calculating reach (distance propagation) within shaders involves efficiently measuring and utilizing fragment distances.

Core Distance Calculation

Fragment shaders primarily measure distance between the current fragment and a specific point (e.g., UV coordinates). Utilize:

• Euclidean Distance: float dist = distance(*, targetUV); Most common and intuitive.
• Absolute Distance: float dist = abs(*.x - targetUV.x) + abs(*.y - targetUV.y); Faster, approximate for Manhattan-like effects.
• Squared Euclidean: float distSq = dot(deltaUV, deltaUV); Avoids the expensive sqrt, ideal for comparisons or scaled effects.

Sampling for Influence

Determine reach impact using the calculated distance:

• Linear Falloff: float influence = saturate(1.0 - dist / maxReach);
• Non-Linear Falloff: float influence = saturate(1.0 - pow(dist / maxReach, exponent)); (Adjust exponent for curve shape).
• Smoothstep: float influence = smoothstep(maxReach, 0.0, dist); Creates smoother transitions at the boundaries.

Practical Considerations

• Normalization: Normalize UV coordinates when working in screen/texture space for consistent distance scaling.
• Precision & Filtering: Distance calculations near discontinuities or using discard can cause aliasing. Use MIP filtering judiciously or analytical anti-aliasing techniques where applicable.
• Coordinate Space: Choose the most relevant space (World Space, UV Space, Screen Space) for your effect. Transform points accurately into the same space before measuring distance.
• Performance: Minimize vector operations inside loops. Pre-calculate values outside loops where possible. Favor squared distance for comparisons.

Alternative Techniques

• Distance Fields: Precompute a Signed Distance Field (SDF) texture representing distances from a surface. Sample this texture in the shader to achieve very precise reach effects with minimal calculation cost per fragment.
• Compute Shaders: For highly complex propagation requiring iterative analysis or data sharing between pixels, offload calculation to a compute shader and pass the results to rendering shaders.