Beginning Metal - Part 10: Instancing | Ray Wenderlich

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Learn how you can using instancing to render crowd scenes or a field of grass using minimal resources.

This is a companion discussion topic for the original entry at https://www.raywenderlich.com/3537-beginning-metal/lessons/10
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Great tutorial series! Watching the last 3 lessons today.

One code issue in InstanceScene.swift in the video and the download materialsā€¦

In InstanceScene.swift, the outer ā€œfor _ in 0ā€¦<40ā€ loop is not needed after the ā€œfor human in humans.nodesā€ loop is added is it?

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Hello Caroline. Awesome tutorial! I have a question regarding the uint instanceID. Is it possible to create an ā€œinstanceDescriptorā€ and utilize the [stage_in] qualifier as opposed to using the [instance_id] qualifier.

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@twohyjr - Iā€™m not quite sure where your questionā€™s coming from.

The [[ stage_in ]] qualifier is per vertex.

When you use instancing, youā€™re using the same vertex over and over, but just different parameters for each instance.

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Hi Caroline. Great series so far ā€“ thanks!

One problem. I tried following the challenge through but noticed that no grass was appearing (this is using Swift 4 and Xcode 9, beta 6). Tapping ā€˜Capture GPU Frameā€™ I noticed the following issue appears in the instance debug group:

The Compiler was not able to Preload your Buffer
(Issue) The compiler was not able to preload your buffer. Simplify your memory access pattern by using the constant address space, a struct, or a descriptor.

I double checked against the final project included in the chapter resources, only adding the two necessary lines to compile (pipelineDescriptor.depthAttachmentPixelFormat = .depth32Float and metalView.depthStencilPixelFormat = .depth32Float), and Iā€™m seeing the same result ā€“ although the models do display here.

Any ideas?

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Missing grass and the issue above were in fact unrelated.

My grass was just underground. Clearly just needed some watering a.k.a. setting grass.position.z not grass.position.y!

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@cldr - so glad you were able to fix it! It can be very frustrating when the mesh just disappears.

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