FabricateGltfBridge.kt

src/jvmMain/kotlin/afield/graphics/scene/fabricated/FabricateGltfBridge.kt · 70 lines

package afield.graphics.scene.fabricated

import afield.graphics.scene.GltfSupport
import org.lwjgl.assimp.Assimp

The glTF side of the fabricated scene model: one call that turns a loaded GltfSupport.GltfModel into a FabricateScene, and two conversions beside it.

There are two routes from a loaded model into the PBR renderer and they differ in what they touch. FabricateGltfBridge.fromModel builds a scene graph and stops, so a caller can read or rewrite the imported nodes before any GPU resource exists. StandardRenderer.Bundle.registerGltf does that same import and then registers a pulling mesh per node, which is what the renderer draws from and what a tool inspecting node names does not need.

Nothing here loads a file. GltfSupport.loadGltfBasic is the loader and MeshFromDisk.kt describes the route in; this is the conversion at the end of it.

object FabricateGltfBridge

Converts the existing Assimp/GLTF loader model into the fabricated scene/material data model.

object FabricateGltfBridge {

fun fromModel(model: GltfSupport.GltfModel, name: String = "gltf"): FabricateScene

A FabricateScene holding model's meshes, with no renderer and no GPU resources attached.

name is the root node's name and the prefix on every imported node's. FabricateScene.importGltf is this same import with its material classification open as a parameter, and StandardRenderer.Bundle.registerGltf is the import plus the pulling meshes a renderer draws from.

    fun fromModel(model: GltfSupport.GltfModel, name: String = "gltf"): FabricateScene {
        val root = FabricateNode(name)
        val scene = FabricateScene(root)
        scene.importGltf(model, namePrefix = name)
        return scene
    }
}

fun GltfSupport.MaterialTextured.toFabricateMaterial(): FabricateMaterial

FabricateMaterial.fromGltf as an extension, for a glTF material already in hand.

Nothing in the tree calls it. The import path reaches fromGltf through FabricateScene.importGltf's default material lambda instead.

fun GltfSupport.MaterialTextured.toFabricateMaterial(): FabricateMaterial =
    FabricateMaterial.fromGltf(this)

fun Int.toFabricateTextureSemantic(): String

An Assimp texture-type constant as the glTF name for that slot: baseColor, normal, metallicRoughness and so on, with an unrecognised type rendered as texture- and its number rather than dropped.

A label, not a lookup key, and nothing in the tree calls it. FabricateMaterial.fromGltf picks its textures by matching the Assimp constants directly and never consults this, so the baseColor returned here and the baseColor push constant standardRenderer.kt seeds are one word for two unrelated things.

fun Int.toFabricateTextureSemantic(): String = when (this) {
    Assimp.aiTextureType_BASE_COLOR -> "baseColor"
    Assimp.aiTextureType_DIFFUSE -> "diffuse"
    Assimp.aiTextureType_NORMALS -> "normal"
    Assimp.aiTextureType_EMISSIVE -> "emissive"
    Assimp.aiTextureType_METALNESS -> "metallic"
    Assimp.aiTextureType_DIFFUSE_ROUGHNESS -> "roughness"
    Assimp.aiTextureType_GLTF_METALLIC_ROUGHNESS -> "metallicRoughness"
    Assimp.aiTextureType_AMBIENT_OCCLUSION -> "occlusion"
    Assimp.aiTextureType_LIGHTMAP -> "lightmap"
    Assimp.aiTextureType_CLEARCOAT -> "clearcoat"
    else -> "texture-$this"
}