The performance optimization with post rendering.(like scale rendering).

1. Performance optimization
with post rendering
AkilarLiao

2. Outline
1. Why do we need post rendering?
2. Mobile device pixel fill rate issue
3. How the post rendering improves performance?
4. Preview demo
5. Performace analysis
6. What is post rendering?
7. How does it work?
8. Projected point UV
9. Projected texture reference code
10.Change screen size vs post rendering
11.Linear texture filtering problem
12.Where is the COF project applied?
13.Summary

3. Why do we need post rendering?
1. Full screen pixel processing performance issues, such as water, clouds,
terrain ... and so on.
2. Reducing screen resolution to reduce pixel processing isn’t an option.
(for example, I hope the UI to maintain the native resolution of the
device).
3. In short, just reduce the pixel resolution.

4. Mobile device pixel fill rate issue
Visible screen cellActual pixel resolution

5. Mobile Pixel-Filling rate issue
✓OK
✗Not OK

6. How the post rendering improves performance?
Complex fragment
shader
Complex fragment
shader
Complex fragment
shader
Complex fragment
shader
Complex fragment
shader
(1920X1080)
Only paste one texture
fragment shader
1920X1080 = 2073600
1024X512 = 524800
+ simple shader(1024X512)

7. Preview demo
Preview demo

8. Splatting plane to DirectViewPort

9. Splatting plane with PostRendering (1024)

10. Dynamic Clouds to DirectViewPort

11. Dynamic Clouds with PostRendering (512)

12. Ocean plane to DirectViewPort

13. Ocean Plane with PostRendering (1024)

14. Splatting and Clouds to DirectViewPort

15. Splatting and Clouds with PostRendering

16. Ocean and Clouds to DirectViewPort

17. Ocean and Clouds to PostRendering

18. Performance analysis
RedMi Note3 DirectViewPort PostRendering RTTSize
Splatting plane 45 60 1024
Clouds 60 60 512
Ocean 43 59 1024
Splatting plane
+ Clouds
36 56
Ocean+Clouds 35 52

19. What is post rendering?
Render an object to texture (RTT), process
shader in this RTT , and then render it
once again with projected UV(so, render
twice).

20. How does it work?
RTT Result
Final Result
Plane

21. Projected point UV

22. Projected texture reference code - vertex shader
#include "UnityCG.cginc"
struct ProjectedTextureVertexInput{
float4 Vertex : POSITION;
};
struct ProjectedTextureVertexOutput{
float4 Vertex : SV_POSITION;
float4 UVProjection : TEXCOORD0;
};
uniform sampler2D _ProjectedTexture;
ProjectedTextureVertexOutput ProjectedTextureVertexProgram(ProjectedTextureVertexInput Input){
ProjectedTextureVertexOutput Output;
Output.Vertex = UnityObjectToClipPos(Input.Vertex);
Output.UVProjection = ComputeScreenPos(Output.Vertex);
return Output;
}

23. Projected texture reference code - fragment
shader
…
Output.UVProjection = ComputeScreenPos(Output.Vertex);
…
fixed4 ProjectedTextureFragmentProgram(ProjectedTextureVertexOutput Input) : SV_Target{
half2 ProjectionCoord = (Input.UVProjection / Input.UVProjection.w).xy;
return tex2D(_ProjectedTexture, ProjectionCoord);
}

24. Change screen size vs post rendering
Advantage Weakness
Change screen size
1. Draw once。
2. Without any RTT and other
camera processing。
1. Only one Resolution,
can not be individually
optimized。
2. Can not be applied to
situations where native
resolution needs to be
keeped (Example UI)。
Post rendering
1. Keep the native resolution,
not affect the resolution
requirements (such as UI)
2. Provide different resolutions
for individual objects。
1. Draw twice。
2. extra RTT and camera

25. Linear texture filter problem

26. Direct render to view port is correct

27. Where is the COF project applied
Cloud system
Ocean system

28. Summry
Timing
○ When dealing with objects covering full screen, and the
fragment shader is too complicated.
○ When screen resolution can not be reduced or want to have
separate pixel resolution.
PS
● Linear textue filter problem.
● Use RenderTexture.GetTemporary and
RenderTextue.Release.

29. Thanks