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There is a CAMediaTimingFunction. (This is the easing of easeInQuart.)
let timingFunction = CAMediaTimingFunction(controlPoints: 0.895, 0.03, 0.685, 0.22)
I want to pass a time in the range [0, 1] to this timingFunction to get an output in the range [0, 1].
For example, if I pass 0.5, it should output a value smaller than 0.5 because it is easeInQuart (slow at first).
Is this possible?
Thanks.
Goal: Define the normal vector for a plane represented by SCNPlane.
As mentioned in Apple's documentation Working with Vectors - Calculate the Normal of a Triangle, I can calculate the normal vector based on 3 points from the plane. The issue here is that I don't know how I can get 3 points that they make proper triangle. I've noticed that SCNPlane has a property boundingBox and it can represent 2 of the triangle vertices (min and max). How can I find the 3rd vertex that is placed on the SCNPlane? I cannot use the center of the SCNPlane, because it creates a line along with min and max points from boundingBox.
Is there any other way that can help me to retrieve a normal vector for the SCNPlane?
From the documentation we learn that
The surface is one-sided. Its surface normal vectors point in the positive z-axis direction of its local coordinate space, so it is only visible from that direction by default.
The normal of a SCNPlane is always (0, 0, 1) in local space and that cannot change.
When it is attached to a node, the orientation of that node determines the normal in an another coordinate system. You can use simdConvertVector:toNode: to convert between coordinate spaces:
// normal expressed in world space
let normal = simd_normalize(node.simdConvertVector(simd_float3(0, 0, 1), to: nil))
To add to the accepted answer, in order to retrieve the points that define the plane, you can query the plane's geometry sources.
let plane = SCNPlane(width: 100, height: 20)
print("Sources for normal: \(vertices(sources: plane.sources(for: .normal)))")
print("Sources for vertex: \(vertices(sources: plane.sources(for: .vertex)))")
extension UnsafeRawPointer {
func loadUnaligned<T>(as: T.Type, count: Int) -> [T] {
assert(_isPOD(T.self)) // relies on the type being POD (no refcounting or other management)
let buffer = UnsafeMutablePointer<T>.allocate(capacity: count)
defer { buffer.deallocate() }
memcpy(buffer, self, MemoryLayout<T>.size * count)
return (0..<count).map({ index in buffer.advanced(by: index).pointee })
}
}
func vertices(sources: [SCNGeometrySource]) -> [[SCNVector3]] {
var result = [[SCNVector3]]()
result.reserveCapacity(sources.count)
for source in sources {
precondition(source.usesFloatComponents == true, "SCNVector3 can handle only three-component vectors whose components are floating-point values, i.e., floats or doubles")
precondition(source.componentsPerVector == 3, "SCNVector3 can only be used for three components per vector")
let shouldUseFloatNotDouble: Bool
if source.bytesPerComponent == 4 {
shouldUseFloatNotDouble = true
}
else if source.bytesPerComponent == 8 {
shouldUseFloatNotDouble = false
}
else {
assert(false, "The SCNGeometrySource has reported an unexpected byte size for its vector components, not 4 bytes (float) or 8 bytes (double) but \(source.bytesPerComponent). I am not equipped for this so I am going to use floats and hope for the best. This will probably not work. Sorry.")
shouldUseFloatNotDouble = true
}
let vectors = source.data.withUnsafeBytes {
(p: UnsafeRawBufferPointer) -> [SCNVector3] in
if (shouldUseFloatNotDouble) {
let simdArray = (p.baseAddress! + source.dataOffset).loadUnaligned(as: SIMD3<Float>.self, count: source.vectorCount)
return simdArray.map { simd in SCNVector3(simd)}
} else {
let simdArray = (p.baseAddress! + source.dataOffset).loadUnaligned(as: SIMD3<Double>.self, count: source.vectorCount)
return simdArray.map { simd in SCNVector3(simd)}
}
}
result.append(vectors)
}
return result
}
Output:
Sources for normal: [[__C.SCNVector3(x: 0.0, y: 0.0, z: 1.0), __C.SCNVector3(x: 1.0, y: 0.5, z: -0.5), __C.SCNVector3(x: 0.0, y: 0.0, z: 1.0), __C.SCNVector3(x: 1.0, y: -0.5, z: 0.5)]]
Sources for vertex: [[__C.SCNVector3(x: -0.5, y: -0.5, z: 0.0), __C.SCNVector3(x: 0.0, y: 1.0, z: 0.0), __C.SCNVector3(x: 0.5, y: -0.5, z: 0.0), __C.SCNVector3(x: 0.0, y: 1.0, z: 1.0)]]
I am totally new to tessellation and relatively new to Metal API, and have been referring to this sample code https://developer.apple.com/library/archive/samplecode/MetalBasicTessellation/Introduction/Intro.html
I realise the max tessellation factor on iOS is 16, which is very low for my use case compared to 64 on OSX.
I suppose i'll need to apply tessellation on a quad that has been sub-divided to 4 by 4 smaller sections to begin with, so that after tessellation it will end up into something like one with a tessellation factor of 64?
So, i've changed the input control points to something like this
static const float controlPointPositionsQuad[] = {
-0.8, 0.8, 0.0, 1.0, // upper-left
0.0, 0.8, 0.0, 1.0, // upper-mid
0.0, 0.0, 0.0, 1.0, // mid-mid
-0.8, 0.0, 0.0, 1.0, // mid-left
-0.8, 0.0, 0.0, 1.0, // mid-left
0.0, 0.0, 0.0, 1.0, // mid-mid
0.0, -0.8, 0.0, 1.0, // lower-mid
-0.8, -0.8, 0.0, 1.0, // lower-left
0.0, 0.8, 0.0, 1.0, // upper-mid
0.8, 0.8, 0.0, 1.0, // upper-right
0.8, 0.0, 0.0, 1.0, // mid-right
0.0, 0.0, 0.0, 1.0, // mid-mid
0.0, 0.0, 0.0, 1.0, // mid-mid
0.8, 0.0, 0.0, 1.0, // mid-right
0.8, -0.8, 0.0, 1.0, // lower-right
0.0, -0.8, 0.0, 1.0, // lower-mid
};
and for the drawPatches i changed it to 16 instead of 4.
But the result is that it is only showing only the first 4 points (top left).
if i change the vertex layout stride to this:
vertexDescriptor.layouts[0].stride = 16*sizeof(float);
it is still showing the same.
I don't really know what i'm doing but what i'm going for is similar to tessellating a 3d mesh, but for my case is just a quad with subdivisions.
I am unable to find any tutorial / code samples that teach about this using Metal API.
Can someone please point me to the right direction? thanks!
Here are a few things to check:
Ensure that your tessellation factor compute kernel is generating inside/edge factors for all patches by dispatching a compute grid of the appropriate size.
When dispatching threadgroups to execute your tessellation factor kernel, use 1D threadgroup counts and sizes (such that the total thread count is the number of patches, and the heights of both sizes passed to the dispatch method are 1).
When drawing patches, the first parameter (numberOfPatchControlPoints) should equal the number of control points in each patch (3 for triangles; 4 for quads), and the third parameter should be the number of patches to draw.
In the SSD512 object detection model the default values of aspect_ratios are :
aspect_ratios_per_layer=[[1.0, 2.0, 0.5],
[1.0, 2.0, 0.5, 3.0, 1.0/3.0],
[1.0, 2.0, 0.5, 3.0, 1.0/3.0],
[1.0, 2.0, 0.5, 3.0, 1.0/3.0],
[1.0, 2.0, 0.5, 3.0, 1.0/3.0],
[1.0, 2.0, 0.5],
[1.0, 2.0, 0.5]],
But i want to have these values : [1.0 , 1.0/4.0 , 1.0/3.0 , 0.5 , 3.0/4.0 ]
Now i want to replace these values with my own values , How do I add these to the layers? Why in the first layer don't exist 1.0/3.0 value and so on , What are the rules for the layers selected?
let's take this example:
we use X and Y data corresponding to the known polynomial f (x) = 0.25 - x + x2. Using POLY_FIT to compute a second degree polynomial fit returns the exact coefficients (to within machine accuracy).
; Define an 11-element vector of independent variable data:
X = [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0]
; Define an 11-element vector of dependent variable data:
Y = [0.25, 0.16, 0.09, 0.04, 0.01, 0.00, 0.01, 0.04, 0.09, $
0.16, 0.25]
; Define a vector of measurement errors:
measure_errors = REPLICATE(0.01, 11)
; Compute the second degree polynomial fit to the data:
result = POLY_FIT(X, Y, 2, MEASURE_ERRORS=measure_errors, $
SIGMA=sigma)
; Print the coefficients:
PRINT, 'Coefficients: ', result
PRINT, 'Standard errors: ', sigma
this example prints,
Coefficients: 0.250000 -1.00000 1.00000
Standard errors: 0.00761853 0.0354459 0.0341395
that works as expected, but let say I already know the coefficient 0.25, how can I pass to POLY_FIT that coefficient ? or maybe I have to use some other FIT function ?
source: http://www.exelisvis.com/docs/POLY_FIT.html
Have you looked at MPFIT? It has keywords to pass information about the parameters. Docs.