I am trying to make unity render lots of (1M) cubes all with different rotation, position and color. Position and color work fine, but the rotations are somehow calculated wrong. It manifests mostly when I rotate them around the x or z axes over 180 degrees. Here is my code:
Shader "Instanced/InstancedSurfaceShader" {
Properties {
_MainTex ("Albedo (RGB)", 2D) = "white" {}
_Glossiness ("Smoothness", Range(0,1)) = 0.5
_Metallic ("Metallic", Range(0,1)) = 0.0
}
SubShader {
Tags { "RenderType"="Opaque" }
LOD 200
CGPROGRAM
// Physically based Standard lighting model
#pragma surface surf Standard addshadow fullforwardshadows
#pragma multi_compile_instancing
#pragma instancing_options procedural:setup
sampler2D _MainTex;
struct Input {
float2 uv_MainTex;
};
#ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED
StructuredBuffer<float4> positionBuffer;
StructuredBuffer<float4> colorBuffer;
StructuredBuffer<float4> rotationBuffer;
#endif
void setup()
{
#ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED
float4 position = positionBuffer[unity_InstanceID];
float4 q = rotationBuffer[unity_InstanceID];
float qr = q[0];
float qi = q[1];
float qj = q[2];
float qk = q[3];
float4x4 rotation;
float4x4 translation = {
1,0,0,position.x,
0,1,0,position.y,
0,0,1,position.z,
0,0,0,1
};
// quaternion to matrix
// http://www.euclideanspace.com/maths/geometry/rotations/conversions/quaternionToMatrix/
// https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation#Quaternion-derived_rotation_matrix
rotation[0][0] = 1.0f - 2.0f*qj*qj - 2.0f*qk*qk;
rotation[0][1] = 2.0f*(qi*qj - qk*qr);
rotation[0][2] = 2.0f*(qi*qk + qj*qr);
rotation[0][3] = 0.0f;
rotation[1][0] = 2.0f*(qi*qj+qk*qr);
rotation[1][1] = 1.0f - 2.0f*qi*qi - 2.0f*qk*qk;
rotation[1][2] = 2.0f*(qj*qk - qi*qr);
rotation[1][3] = 0.0f;
rotation[2][0] = 2.0f*(qi*qk - qj*qr);
rotation[2][1] = 2.0f*(qj*qk + qi*qr);
rotation[2][2] = 1.0f - 2.0f*qi*qi - 2.0f*qj*qj;
rotation[2][3] = 0.0f;
rotation[3][0] = 0.0f;
rotation[3][1] = 0.0f;
rotation[3][2] = 0.0f;
rotation[3][3] = 1.0f;
unity_ObjectToWorld = mul(translation, rotation);
//unity_WorldToObject = inverse(unity_ObjectToWorld);
// inverse transform matrix
// taken from richardkettlewell's post on
// https://forum.unity3d.com/threads/drawmeshinstancedindirect-example-comments-and-questions.446080/
float3x3 w2oRotation;
w2oRotation[0] = unity_ObjectToWorld[1].yzx * unity_ObjectToWorld[2].zxy - unity_ObjectToWorld[1].zxy * unity_ObjectToWorld[2].yzx;
w2oRotation[1] = unity_ObjectToWorld[0].zxy * unity_ObjectToWorld[2].yzx - unity_ObjectToWorld[0].yzx * unity_ObjectToWorld[2].zxy;
w2oRotation[2] = unity_ObjectToWorld[0].yzx * unity_ObjectToWorld[1].zxy - unity_ObjectToWorld[0].zxy * unity_ObjectToWorld[1].yzx;
float det = dot(unity_ObjectToWorld[0], w2oRotation[0]);
w2oRotation = transpose(w2oRotation);
w2oRotation *= rcp(det);
float3 w2oPosition = mul(w2oRotation, -unity_ObjectToWorld._14_24_34);
unity_WorldToObject._11_21_31_41 = float4(w2oRotation._11_21_31, 0.0f);
unity_WorldToObject._12_22_32_42 = float4(w2oRotation._12_22_32, 0.0f);
unity_WorldToObject._13_23_33_43 = float4(w2oRotation._13_23_33, 0.0f);
unity_WorldToObject._14_24_34_44 = float4(w2oPosition, 1.0f);
#endif
}
half _Glossiness;
half _Metallic;
UNITY_INSTANCING_BUFFER_START(Props)
UNITY_DEFINE_INSTANCED_PROP(fixed4, _Color)
UNITY_INSTANCING_BUFFER_END(Props)
void surf (Input IN, inout SurfaceOutputStandard o) {
fixed4 c = {0,0,255,0};//tex2D (_MainTex, IN.uv_MainTex);
#ifdef UNITY_PROCEDURAL_INSTANCING_ENABLED
c=colorBuffer[unity_InstanceID];
#endif
o.Albedo = c.rgb;
o.Metallic = _Metallic;
o.Smoothness = _Glossiness;
o.Alpha = c.a;
}
ENDCG
}
FallBack "Diffuse"
}
Maybe something wrong with the matrix calculations?
