setIBLRotation:: how to get the rotation matrix in vertex block

[JackKaiXing]

Hello @romainguy ,

This discussion origins from issue #3951.

Let me describe what we are trying to achieve.

---

VBO
position attribute in world space
{0.0, 0.0, 0.0},{0.0, 0.0, 0.0},{1.0, 0.0, 0.0},{1.0, 0.0, 0.0}
custom attribute in world space,
{0.0, -1.0, 0.0},{0.0, 1.0, 0.0},{0.0, -1.0, 0.0},{0.0, 1.0, 0.0};

IBO
{0,2,3, 0,3,1};

Material Parameter
width : float type

vertex block

vec4 pos = material.worldPosition;
vec2 dir = getCustom0().xy;
material.worldPosition = vec4(pos.x + dir.x * width, pox.y + dir.y * width, pos.z, pos.w);

---

It works fine without setIBLRotation. What could help if I setIBLRotation?

Any other solution besides passing rotation matrix to vertex block?

[romainguy]

I'm still not sure what you are trying to do. You could pass the ibl rotation as a parameter indeed, it's a single value since the rotation is constrained to the Y axis.

Are you trying to keep a rectangle aligned to the camera? If so you may want to simply use a different vertex domain so you wouldn't have to deal with the IBL rotation at all.

[JackKaiXing]

1. what we are trying to do is to draw a Polyline with varying width at runtime.

   as the vbo, ibo listed above, if width= 2
   the final vertex world position is {0.0, -2.0, 0.0},{0.0, 2.0, 0.0},{1.0, -2.0, 0.0},{1.0, 2.0, 0.0}

   as the vbo, ibo listed above, if width= 3
   the final vertex world position is {0.0, -3.0, 0.0},{0.0, 3.0, 0.0},{1.0, -3.0, 0.0},{1.0, 3.0, 0.0}

2. setIBLRotation uses an axis and radians, is it a constrained to the Y axis?