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++ // Copyright (C) 2023 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
++
++ vec2 qt_parallaxMapping(in vec2 uv,
++ in sampler2D heightMap,
++ in vec3 tangent,
++ in vec3 binormal,
++ in vec3 normal,
++ in vec3 vertex,
++ in vec3 cameraPosition,
++ in float depthScale,
++ in float minLayers,
++ in float maxLayers)
++ {
++ mat3 tanFrame = transpose(mat3(tangent, binormal, normal));
++ vec3 viewDir = normalize(tanFrame * vertex - tanFrame * cameraPosition);
++ float numLayers = mix(float(maxLayers), float(minLayers), abs(dot(vec3(0.0, 0.0, 1.0), viewDir)));
++ float layerDepth = 1.0 / numLayers;
++ float currentLayerDepth = 0.0;
++ vec2 P = viewDir.xy * depthScale;
++ vec2 delta = P / numLayers;
++ vec2 offset = uv;
++ float depth = textureLod(heightMap, offset, 0.0).r;
++ float currentDepth = 0.0;
++ while (currentDepth < depth)
++ {
++ offset -= delta;
++ depth = textureLod(heightMap, offset, 0.0).r;
++ currentDepth += layerDepth;
++ }
++ vec2 prevOffset = offset + delta;
++ float afterDepth = depth - currentDepth;
++ float beforeDepth = textureLod(heightMap, prevOffset, 0.0).r - currentDepth + layerDepth;
++ float weight = afterDepth / (afterDepth - beforeDepth);
++ return mix(offset, prevOffset, weight);
++ }