VirtualTexture

Introduction

Virtual texture for unity.

Run The Demo

1. Open the project with Unity 2018(or later).
2. Click "Menu -> Demo -> Generate Virtual Texture" to generate needed data, it may takes about 10 minutes.
3. Open Demo Scene.
4. Play. Use w/s/a/d and mouse to move the camera.

Screenshot1	Screenshot2

Implement Detail

component	output
Feedback Renderer
Feedback Reader
Tiled Texture
Page Table
Screenshot

1. Feedback Renderer

Render the scene with feedback shader:

fixed4 VTFragFeedback(VTV2f i) : SV_Target
{
	float2 page = floor(i.uv * _VTFeedbackParam.x);
	float2 uv = i.uv * _VTFeedbackParam.y;
	float2 dx = ddx(uv);
	float2 dy = ddy(uv);
	int mip = clamp(int(0.5 * log2(max(dot(dx, dx), dot(dy, dy))) + 0.5 + _VTFeedbackParam.w), 0, _VTFeedbackParam.z);

	return fixed4(page / 255.0, mip / 255.0, 1);
}

2. Feedback Reader

Readback feedback texture from gpu to cpu.

3. Tiled Texture

Load all need texture tiles into TiledTexture.

4. Page Table

update page table and lookup texture.

5. Shading

fixed4 VTFragUnlit(VTV2f i) : SV_Target
{
	float2 uv = VTTransferUV(i.uv);
	fixed4 col = VTTex2D0(uv);
	return col;
}

float2 VTTransferUV(float2 uv)
{
	float2 uvInt = uv - frac(uv * _VTPageParam.x) * _VTPageParam.y;
	fixed4 page = tex2D(_VTLookupTex, uvInt) * 255;
	float2 inPageOffset = frac(uv * exp2(_VTPageParam.z - page.b));
	float2 inTileOffset = inPageOffset * _VTTileParam.y + _VTTileParam.x;
	return (page.rg + inTileOffset) * _VTTileParam.zw;
}

fixed4 VTTex2D0(float2 uv)
{
	return tex2D(_VTTiledTex0, uv);
}

Reference

http://www.silverspaceship.com/src/svt/