Goal: To render in an apple vision pro app, the solid-mechanics 3D simulation results coming form an FEA code.
Starting point: I have surface vtks with deformations on each node. Each time step has a a mesh with the nodal coordinates. This is straighforward translatable to a usd MeshSequence. Unfortunately, the results cannot be simplified to a scaling o linear transformation as you would do with other game-oriented animations.
Tools: Right now, I am using Xcode and reality composer pro (RCP) to build the scenes.
Technical limitations: I am aware that RCP can do animations with BlendMesh and skeletons and that MeshSequence is not a problem.
Progress:
Coverting to the sequence of vtk meshes to a usd MeshSequence is straighforward. This animates correctly in Preview and Blender (see screenshot).
I managed to convert from MeshSequence to multiple keys and BlendMesh. This also animates correctly in Blender and preview. Unfortunately, the BlendMesh of multiple blended meshes shows a zero animation time in RCP (see screenshot below)
Also, see below usda file scheme for the animation. Of course I am not showing full vectors such as faceVertexCounts, faceVertexIndex, normals.
Question: what is the right set up to create a BlendMesh animation that RCP will correctly import and animate, form a set of Meshes or multiple key shapes?
Blender animation
Time zero RCP "animations"
#usda 1.0
(
defaultPrim = "BlendMeshRoot"
doc = "Blender v4.5.3 LTS"
endTimeCode = 48
framesPerSecond = 24
metersPerUnit = 1
startTimeCode = 0
timeCodesPerSecond = 24
upAxis = "Z"
)
def Xform "BlendMeshRoot" (
customData = {
dictionary Blender = {
bool generated = 1
}
}
)
{
def SkelRoot "Mesh"
{
custom string userProperties:blender:object_name = "Mesh"
float3 xformOp:rotateXYZ = (89.99999, -0, 0)
float3 xformOp:scale = (0.009999999, 0.01, 0.01)
double3 xformOp:translate = (0, 0, 0)
uniform token[] xformOpOrder = ["xformOp:translate", "xformOp:rotateXYZ", "xformOp:scale"]
def Mesh "Mesh" (
active = true
prepend apiSchemas = ["MaterialBindingAPI", "SkelBindingAPI"]
)
{
uniform bool doubleSided = 1
float3[] extent = [(25.091871, -34.121277, -13.298501), (299.94482, 245.10088, 202.35126)]
int[] faceVertexCounts = [3, 3, ...
int[] faceVertexIndices = [0, 10293, ...
rel material:binding = </BlendMeshRoot/_materials/MeshSequence_Default>
normal3f[] normals = [(-0.3632836, -0.9102419, -0.19870725), ....
point3f[] points = [(244.41148, 155.42062, 70.454926),.....
float3[] primvars:node_displacement = [(93.54703, 110.9341, 48.37992)....
float3[] primvars:Normals = [(-0.0050530406, -0.9910114, -0.13368203),...
int[] primvars:skel:jointIndices = [0, 0, 0, 0, 0 ...
float[] primvars:skel:jointWeights = [1, 1, 1, 1, 1...
uniform token[] skel:blendShapes = ["frame_0000", "frame_0001", "frame_0002", "frame_0003", "frame_0004", "frame_0005"]
rel skel:blendShapeTargets = [
</BlendMeshRoot/Mesh/Mesh/frame_0000>,
.......
</BlendMeshRoot/Mesh/Mesh/frame_0005>,
]
prepend rel skel:skeleton = </BlendMeshRoot/Mesh/Skel>
uniform token subdivisionScheme = "none"
custom string userProperties:blender:data_name = "Mesh"
custom float userProperties:originalTime
float userProperties:originalTime.timeSamples = {
0: 0,
}
def BlendShape "frame_0000"
{
uniform vector3f[] offsets = [(0, 0, 0), (0, 0, 0),.....
uniform int[] pointIndices = [0, 1, 2, .....
}
.....
.....
#### BlendShape frame to 0005
.....
def Skeleton "Skel" (
prepend apiSchemas = ["SkelBindingAPI"]
)
{
uniform matrix4d[] bindTransforms = [( (1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), (0, 0, 0, 1) )]
uniform token[] joints = ["joint1"]
uniform matrix4d[] restTransforms = [( (1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), (0, 0, 0, 1) )]
prepend rel skel:animationSource = </BlendMeshRoot/Mesh/Skel/Anim>
def SkelAnimation "Anim"
{
uniform token[] blendShapes = ["frame_0000", "frame_0001", "frame_0002", "frame_0003", "frame_0004", "frame_0005"]
float[] blendShapeWeights.timeSamples = {
0: [1, 0, 0, 0, 0, 0],
1: [0.9697085, 0.03029152, 0, 0, 0, 0],
2: [0.88787615, 0.11212383, 0, 0, 0, 0],
.....
46: [0, 0, 0, 0, 0.11212379, 0.8878762],
47: [0, 0, 0, 0, 0.030291557, 0.96970844],
48: [0, 0, 0, 0, 0, 1],
}
}
}
}
def Scope "_materials"
{
def Material "MeshSequence_Default"
{
token outputs:surface.connect = </BlendMeshRoot/_materials/MeshSequence_Default/Principled_BSDF.outputs:surface>
custom string userProperties:blender:data_name = "MeshSequence_Default"
def Shader "Principled_BSDF"
{
uniform token info:id = "UsdPreviewSurface"
float inputs:clearcoat = 0
float inputs:clearcoatRoughness = 0.03
color3f inputs:diffuseColor = (0.8, 0.4, 0.3)
float inputs:ior = 1.5
float inputs:metallic = 0
float inputs:opacity = 1
float inputs:roughness = 0.5
float inputs:specular = 0.2
token outputs:surface
}
}
}
def Scope "AnimationClips"
{
custom rel animations = </BlendMeshRoot/Mesh/Skel/Anim>
}
def RealityKitComponent "AnimationLibrary"
{
custom rel animations = </BlendMeshRoot/Mesh/Skel/Anim>
custom token info:id = "RealityKit.AnimationLibrary"
custom double realitykit:approximateDuration = 2
custom double[] realitykit:clipDurations = [2]
custom string[] realitykit:clipNames = ["Anim"]
custom rel realitykit:clipTargets = </BlendMeshRoot/Mesh/Skel/Anim>
custom double realitykit:frameRate = 24
custom bool realitykit:isAnimationLibrary = 1
}
}