Spielwiese/grass-rendering-prototype
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fix normals

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Timo Eberl 2025-08-31 16:54:24 +02:00
parent 10f57041f9
commit 3b1f2d4073
Signed by: Timo
SSH Key Fingerprint: SHA256:swVjhbVzKCLQZNtwPqMEmtOUG3FTydzVrpIKpUZYTQw
4 changed files with 73 additions and 174 deletions
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106
Assets/Scenes/SampleScene.unity
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2
Assets/Shaders/GrassBlade.shader
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@ -24,7 +24,7 @@
}
SubShader {
LOD 100
// Cull Off
Cull Off
//Render Pass
Pass {

135
Assets/Shaders/include/GrassBladePass.hlsl
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@ -24,7 +24,7 @@ struct v2g {
struct g2f {
float4 pos : SV_POSITION;
#ifdef IS_IN_BASE_PASS
float3 normal : NORMAL;
float3 localNormal : NORMAL;
float2 uv : TEXCOORD0; // bottom left 0.0 top right 1.1 (values converge - 0 and 1 meet at the tip)
SHADOW_COORDS(1) // put shadows data into TEXCOORD1
float3 worldPos : TEXCOORD2;
@ -40,10 +40,6 @@ v2g vert (MeshData v) {
return o;
}
float getCameraDistance(float3 pos) {
return distance(_MainCameraPosition, pos);
}
#if _LOD_LOD_0
[MaxVertexCount(4 + ( 11 - 1 ) * 2)]
#elif _LOD_LOD_1
@ -56,7 +52,6 @@ float getCameraDistance(float3 pos) {
void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
const float3 basePos = IN[0].vertex.xyz;
const float3 tipOffset = IN[0].tipOffset;
const float3 tipPosObjectSpace = basePos + tipOffset;
// const float4 basePosClipSpace = UnityObjectToClipPos(float4(basePos, 1));
// const float4 tipPosClipSpace = UnityObjectToClipPos(float4(tipPosObjectSpace, 1));
@ -64,9 +59,9 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
const float3 basePosWS = mul(unity_ObjectToWorld, float4(basePos.xyz, 1.0)).xyz;
const float cameraDistance = getCameraDistance(basePosWS);
const float mainCamDist = distance(_MainCameraPosition, basePosWS);
float interpolator = invLerp(_TransitionRange.x, _TransitionRange.y, cameraDistance);
float interpolator = invLerp(_TransitionRange.x, _TransitionRange.y, mainCamDist);
float halfWidth = _BladeWidth/2;
@ -78,18 +73,16 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
}
// randomly shrink shadow blades to create a smooth transition between shadowed and non-shadowed area
#ifdef IS_IN_SHADOW_PASS
#if _LOD_LOD_1
#ifdef IS_IN_SHADOW_PASS
#if _LOD_LOD_1
float widthMultiplier = remap(N21(basePos.xz) * 0.5, 1, 1, 0, interpolator);
widthMultiplier = max(0, widthMultiplier);
halfWidth *= widthMultiplier;
#endif
#endif
#endif
#endif
g2f o;
o.debug = float3(0,0,0);
float3 previousSegmentCenter = basePos - float3(0,-1,0); // point beneath the basePos
int numSegments;
#if _LOD_LOD_0
@ -102,13 +95,12 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
numSegments = 1;
#endif
float3 localCameraPos = mul(unity_WorldToObject, float4(_MainCameraPosition.xyz, 1.0)).xyz;
const float lowerThickness = 0.8;
// LOD 3 has a different algorithm
#if _LOD_LOD_3
const float segmentWidth = halfWidth * pow(sin(lowerThickness * 3.141), .8);
const float3 widthOffset = getWidthOffset(segmentWidth, tipOffset.xz) * max(1, cameraDistance / 10);
const float3 widthOffset = getWidthOffset(tipOffset.xz) * segmentWidth * max(1, mainCamDist / 10);
float3 segmentCenterBase = basePos;
float3 segmentCenterTip = basePos + tipOffset;
const float3 vertLeftBase = segmentCenterBase + widthOffset * 2.5;
@ -118,22 +110,13 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
const float3 surfTangent1 = vertRightBase - segmentCenterTip;
const float3 surfTangent2 = vertLeftBase - segmentCenterTip;
const float3 normal = normalize(cross(surfTangent1, surfTangent2)); // TODO remove normalize
float3 normalWS = UnityObjectToWorldNormal(normal);
const float3 camVec = normalize(segmentCenterTip - localCameraPos);
// at which side of the blade are we looking?
const bool lookingFromAbove = dot(camVec, normal) > 0;
if (lookingFromAbove) {
// normalWS = -normalWS;
}
const float3 normal = cross(surfTangent1, surfTangent2);
o.pos = UnityObjectToClipPos(vertRightBase);
#ifdef IS_IN_BASE_PASS
o.uv = float2(1, 0);
TRANSFER_SHADOW(o)
o.normal = normalWS;
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(vertRightBase,1.0)).xyz;
#endif
triStream.Append(o);
@ -142,7 +125,7 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
#ifdef IS_IN_BASE_PASS
o.uv = float2(0, 0);
TRANSFER_SHADOW(o)
o.normal = normalWS;
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(vertLeftBase,1.0)).xyz;
#endif
triStream.Append(o);
@ -151,7 +134,7 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
#ifdef IS_IN_BASE_PASS
o.uv = float2(1, 1);
TRANSFER_SHADOW(o)
o.normal = normalWS;
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(vertRightTip,1.0)).xyz;
#endif
triStream.Append(o);
@ -160,83 +143,105 @@ void geom(point v2g IN[1], inout TriangleStream<g2f> triStream) {
#ifdef IS_IN_BASE_PASS
o.uv = float2(0, 1);
TRANSFER_SHADOW(o)
o.normal = normalWS;
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(vertLeftTip,1.0)).xyz;
#endif
triStream.Append(o);
#else
for (int i = 0; i < numSegments; i++) {
// in "blade space"
const float segmentWidth = halfWidth * pow(sin(lowerThickness * 3.141 * (numSegments - i) / numSegments), .8);
const float segmentHeightNormalized = i / (float)numSegments;
// float nextSegmentHeightNormalized = (i+1) / (float)numSegments;
const float3 widthOffset = getWidthOffset(tipOffset.xz) * max(1, mainCamDist / 10);
// generate new verts
const float3 widthOffset = getWidthOffset(segmentWidth, tipOffset.xz) * max(1, cameraDistance / 10);
float3 segmentCenter = basePos + bendParabula(tipOffset, segmentHeightNormalized, _BendStrength);
const float3 segmentCenterSnapshot = segmentCenter;
const float3 vertLeft = segmentCenter + widthOffset;
const float3 vertRight = segmentCenter - widthOffset;
//const float3 nextSegmentCenter = basePos + bendParabula(tipPos, nextSegmentHeight01);
// previous vertex positions, used for normal calculation
float3 previousVertLeft;
float3 previousVertRight;
for (int i = 0; i < numSegments; i++) {
const float segmentWidth = halfWidth * pow(sin(lowerThickness * 3.141 * (numSegments - i) / numSegments), .8);
const float3 segmentWidthOffset = widthOffset * segmentWidth;
const float segmentHeightNormalized = i / (float)numSegments;
const float3 segmentCenter = basePos + bendParabula(tipOffset, segmentHeightNormalized, _BendStrength);
const float3 vertLeft = segmentCenter + segmentWidthOffset;
const float3 vertRight = segmentCenter - segmentWidthOffset;
#ifdef IS_IN_BASE_PASS
// calculate normal
const float3 surfTangent1 = previousSegmentCenter - segmentCenter;
const float3 surfTangent2 = previousSegmentCenter - vertLeft;
const float3 normal = normalize(cross(surfTangent1, surfTangent2)); // TODO remove normalize
float3 normalWS = UnityObjectToWorldNormal(normal);
const float3 camVec = normalize(segmentCenter - localCameraPos);
// at which side of the blade are we looking?
const bool lookingFromAbove = dot(camVec, normalWS) > 0;
if (lookingFromAbove) {
normalWS = -normalWS;
float3 surfTangent1, surfTangent2;
if (i == 0) {
// for the normals at the bottom vertices, use the normals of the next segment
const float nextSegmentHeightNormalized = (i+1) / (float)numSegments;
const float3 nextSegmentCenter = basePos + bendParabula(tipOffset, nextSegmentHeightNormalized, _BendStrength);
surfTangent1 = nextSegmentCenter - vertRight;
surfTangent2 = nextSegmentCenter - vertLeft;
}
else {
surfTangent1 = segmentCenter - previousVertRight;
surfTangent2 = segmentCenter - previousVertLeft;
}
const float3 normal = cross(surfTangent1, surfTangent2);
// TODO fake curvature
// o.localNormal = normalize(lerp(normalWS, UnityObjectToWorldNormal(-normalize(segmentWidthOffset)), _BladeBow));
previousVertLeft = vertLeft;
previousVertRight = vertRight;
#endif
o.pos = UnityObjectToClipPos(vertRight);
#ifdef IS_IN_BASE_PASS
o.uv = float2(1, segmentHeightNormalized);
TRANSFER_SHADOW(o)
o.normal = normalize(lerp(normalWS, UnityObjectToWorldNormal(-normalize(widthOffset)), _BladeBow));
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(vertRight,1.0)).xyz;
#endif
triStream.Append(o);
previousSegmentCenter = segmentCenterSnapshot;
o.pos = UnityObjectToClipPos(vertLeft);
#ifdef IS_IN_BASE_PASS
o.uv = float2(0, segmentHeightNormalized);
TRANSFER_SHADOW(o)
o.normal = normalize(lerp(normalWS, UnityObjectToWorldNormal(normalize(widthOffset)), _BladeBow));
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(vertLeft,1.0)).xyz;
#endif
triStream.Append(o);
}
#endif
o.pos = UnityObjectToClipPos(basePos + tipOffset * float3(_BendStrength, 1, _BendStrength));
// tip vertex
const float3 tipPosObjectSpace = basePos + tipOffset;
const float3 surfTangent1 = tipPosObjectSpace - previousVertRight;
const float3 surfTangent2 = tipPosObjectSpace - previousVertLeft;
const float3 normal = cross(surfTangent1, surfTangent2);
o.pos = UnityObjectToClipPos(tipPosObjectSpace * float3(_BendStrength, 1, _BendStrength));
#ifdef IS_IN_BASE_PASS
o.uv = float2(.5, 1);
TRANSFER_SHADOW(o)
o.normal = o.normal > 0 ? float3(0, 1, 0) : float3(0, -1, 0);
o.localNormal = normal;
o.worldPos = mul(unity_ObjectToWorld, float4(tipPosObjectSpace,1.0)).xyz;
#endif
triStream.Append(o);
#endif
}
float4 frag(g2f i) : SV_Target{
#ifdef IS_IN_BASE_PASS
float3 localPos = mul(unity_WorldToObject, float4(i.worldPos, 1)).xyz;
float d = distance(localPos, i.debug) * 5;
return float4(i.debug, 1);
float d = distance(localPos, i.debug) * 50;
float k = frac(d);
// return float4(k,k,k, 1);
// return float4(i.debug,1);
float3 worldNormal = UnityObjectToWorldNormal(i.localNormal);
float3 worldViewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
// at which side of the blade are we looking?
// NOT ACCURATE, because the normals don't exactly match the geometry
const bool lookingFromAbove = dot(worldViewDir, worldNormal) > 0;
if (!lookingFromAbove) {
worldNormal = -worldNormal;
}
float3 worldNormal = normalize(i.normal);
float3 lightDirection = normalize(_WorldSpaceLightPos0.xyz);
float3 worldViewDir = normalize(UnityWorldSpaceViewDir(i.worldPos));
float3 worldRefl = reflect(-worldViewDir, worldNormal);
// same as in previous shader

4
Assets/Shaders/include/GrassHelpers.hlsl
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@ -1,7 +1,7 @@
// tipPos2D = xz coordinates of tip
float3 getWidthOffset(float width, float2 tipPos2D) {
float3 getWidthOffset(float2 tipPos2D) {
float2 dirBaseToTip = normalize(tipPos2D);
return float3(-dirBaseToTip.y * width, 0, dirBaseToTip.x * width);
return float3(-dirBaseToTip.y, 0, dirBaseToTip.x);
}
float3 bendParabula(float3 tipPos, float posOnBlade, float bendStrength) {