PathTraceGlassDemo.kt

src/jvmMain/kotlin/afield/graphics/scene/fabricated/PathTraceGlassDemo.kt · 66 lines

package afield.graphics.scene.fabricated

import afield.graphics.vulkan.Renderer
import afield.graphics.vulkan.util.Camera
import afield.math.linalg.Vector3f

All four of the path tracer's glass materials in one scene: clear, absorbing, frosted, and a thin pane.

public/docs/path_tracing.md prints this scene as its glass figure and dev_docs/agents/transcripts/path_tracing_glass.yaml launches it, so what the file builds is what those two are written about. Left to right: a sphere of PathTraceMaterial.glass(), one given an attenuationColor, one given a roughness of 0.32, and a quad of thinGlass.

Most of the geometry here is background, since what a transparent material shows is mostly whatever is behind it. The floor is a checkerboard of 0.55-unit tiles and the wall behind the spheres is eighteen horizontal stripes, both built from the same two diffuse greys, one ten times the reflectance of the other. Each material moves that pattern its own way: refraction displaces the stripes, absorption tints them by how far the ray travelled inside the solid, roughness scatters them, and the thin pane leaves their positions where they are, because thinGlass transmits per crossing and has no thickness to refract across.

The returned renderer is set to ten bounces rather than the default five, because a ray that enters and leaves a sphere has spent two of them before reaching anything else, and to an exposure of 1.5 for a floor this dark. With no environmentPath the light is a constant white environment of radiance one; a path is read by PathTraceEnvironment.fromFile, which takes EXR, Radiance and ordinary image files.

object PathTraceGlassDemo

Clear glass, absorbing green glass, frosted glass and a thin blue pane, from left to right.

object PathTraceGlassDemo {

fun install(renderer: Renderer, environmentPath: String? = null, width: Int = 640, height: Int = 360): PathTracingRenderer

Builds the scene, points a camera at it and installs a PathTracingRenderer under renderer, returning it so a box can blitToScreen or reconfigure it.

    fun install(renderer: Renderer, environmentPath: String? = null, width: Int = 640, height: Int = 360): PathTracingRenderer {
        val scene=PathTraceScene()
        val dark=scene.material(PathTraceMaterial.diffuse(0.055f,0.055f,0.055f))
        val light=scene.material(PathTraceMaterial.diffuse(0.55f,0.55f,0.55f))
        for (x in -10 until 10) for (z in -6 until 8) {
            val a=x*0.55f; val b=z*0.55f; val m=if ((x+z) and 1 == 0) light else dark
            scene.quad(Vector3f(a,0f,b),Vector3f(a,0f,b+0.55f),Vector3f(a+0.55f,0f,b+0.55f),Vector3f(a+0.55f,0f,b),m)
        }
        // Narrow stripes reveal refraction and frosting against a common background.
        for (i in 0 until 18) {
            val y=i*0.18f
            scene.quad(Vector3f(-6f,y,-2.5f),Vector3f(6f,y,-2.5f),Vector3f(6f,y+0.18f,-2.5f),
                Vector3f(-6f,y+0.18f,-2.5f),if (i and 1 == 0) light else dark)
        }
        val clear=scene.material(PathTraceMaterial.glass())
        val green=scene.material(PathTraceMaterial.glass(attenuationColor=Vector3f(0.45f,0.9f,0.65f)))
        val frosted=scene.material(PathTraceMaterial.glass(roughness=0.32f))
        val sheet=scene.material(PathTraceMaterial.thinGlass(tint=Vector3f(0.65f,0.85f,1f)))
        scene.sphere(Vector3f(-2.7f,0.8f,0f),0.8f,clear,48,24)
        scene.sphere(Vector3f(-0.9f,0.8f,0f),0.8f,green,48,24)
        scene.sphere(Vector3f(0.9f,0.8f,0f),0.8f,frosted,48,24)
        scene.quad(Vector3f(2f,0.05f,0.1f),Vector3f(3.4f,0.05f,0.1f),Vector3f(3.4f,1.7f,0.1f),Vector3f(2f,1.7f,0.1f),sheet)
        val camera=Camera(renderer).also { it.at.set(0f,2.7f,9.5f); it.target.set(0f,0.8f,0f); it.p.fov=0.52 }
        return PathTracingRenderer(renderer,scene,environmentPath?.let(PathTraceEnvironment::fromFile)
            ?: PathTraceEnvironment.constant(),width,height,camera).also {
            it.maxBounces=10; it.exposure=1.5f; it.install()
        }
    }
}