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vtfpp: fix bilinear HDRI to cubemap conversion #74

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Merged
merged 2 commits into from
Jun 2, 2025
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vtfpp: fix bilinear HDRI to cubemap conversion #74

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80eb3a6
vtfpp: fix bilinear HDRI to cubemap conversion
koerismo Jun 1, 2025
c8e565a
vtfpp: change cubemap face ordering to match Source envmaps
koerismo Jun 2, 2025
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38 changes: 18 additions & 20 deletions src/vtfpp/ImageConversion.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -852,17 +852,17 @@ void convertHDRIToCubeMapCPUFallback(std::span<const float> imageDataRGBA3232323
for (int row = 0; row < resolution; row++) {
for (int col = 0; col < resolution; col++) {
math::Vec3f pixelDirection3d{
start[0] + ((float) col * 2.f + 0.5f) / (float) resolution * right[0] + ((float) row * 2.f + 0.5f) / (float) resolution * up[0],
start[1] + ((float) col * 2.f + 0.5f) / (float) resolution * right[1] + ((float) row * 2.f + 0.5f) / (float) resolution * up[1],
start[2] + ((float) col * 2.f + 0.5f) / (float) resolution * right[2] + ((float) row * 2.f + 0.5f) / (float) resolution * up[2],
start[0] + (static_cast<float>(col) * 2.f + 0.5f) / static_cast<float>(resolution) * right[0] + (static_cast<float>(row) * 2.f + 0.5f) / static_cast<float>(resolution) * up[0],
start[1] + (static_cast<float>(col) * 2.f + 0.5f) / static_cast<float>(resolution) * right[1] + (static_cast<float>(row) * 2.f + 0.5f) / static_cast<float>(resolution) * up[1],
start[2] + (static_cast<float>(col) * 2.f + 0.5f) / static_cast<float>(resolution) * right[2] + (static_cast<float>(row) * 2.f + 0.5f) / static_cast<float>(resolution) * up[2],
};
float azimuth = std::atan2(pixelDirection3d[0], -pixelDirection3d[2]) + math::pi_f32; // add pi to move range to 0-360 deg
float elevation = std::atan(pixelDirection3d[1] / std::sqrt(pixelDirection3d[0] * pixelDirection3d[0] + pixelDirection3d[2] * pixelDirection3d[2])) + math::pi_f32 / 2.f;
float colHdri = (azimuth / math::pi_f32 / 2.f) * (float) width; // add pi to azimuth to move range to 0-360 deg
float rowHdri = (elevation / math::pi_f32) * (float) height;
float colHdri = (azimuth / math::pi_f32 / 2.f) * static_cast<float>(width); // add pi to azimuth to move range to 0-360 deg
float rowHdri = (elevation / math::pi_f32) * static_cast<float>(height);
if (!bilinear) {
int colNearest = std::clamp((int) colHdri, 0, width - 1);
int rowNearest = std::clamp((int) rowHdri, 0, height - 1);
int colNearest = std::clamp(static_cast<int>(colHdri), 0, width - 1);
int rowNearest = std::clamp(static_cast<int>(rowHdri), 0, height - 1);
face[col * 4 + resolution * row * 4 + 0] = imageDataRGBA32323232F[colNearest * 4 + width * rowNearest * 4 + 0];
face[col * 4 + resolution * row * 4 + 1] = imageDataRGBA32323232F[colNearest * 4 + width * rowNearest * 4 + 1];
face[col * 4 + resolution * row * 4 + 2] = imageDataRGBA32323232F[colNearest * 4 + width * rowNearest * 4 + 2];
Expand Down Expand Up @@ -900,13 +900,11 @@ void convertHDRIToCubeMapCPUFallback(std::span<const float> imageDataRGBA3232323
float f3 = (1 - factorRow) * factorCol;
float f4 = factorRow * factorCol;
for (int j = 0; j < 4; j++) {
auto interpolatedValue = static_cast<uint8_t>(
face[low_idx_column * 4 + width * low_idx_row * 4 + j] * f1 +
face[low_idx_column * 4 + width * high_idx_row * 4 + j] * f2 +
face[high_idx_column * 4 + width * low_idx_row * 4 + j] * f3 +
face[high_idx_column * 4 + width * high_idx_row * 4 + j] * f4
);
face[col * 4 + resolution * row * 4 + j] = std::clamp<uint8_t>(interpolatedValue, 0, 255);
face[col * 4 + resolution * row * 4 + j] =
imageDataRGBA32323232F[low_idx_column * 4 + width * low_idx_row * 4 + j] * f1 +
imageDataRGBA32323232F[low_idx_column * 4 + width * high_idx_row * 4 + j] * f2 +
imageDataRGBA32323232F[high_idx_column * 4 + width * low_idx_row * 4 + j] * f3 +
imageDataRGBA32323232F[high_idx_column * 4 + width * high_idx_row * 4 + j] * f4;
}
}
}
Expand Down Expand Up @@ -1042,12 +1040,12 @@ std::array<std::vector<std::byte>, 6> ImageConversion::convertHDRIToCubeMap(std:
// For each face, contains the 3d starting point (corresponding to left bottom pixel), right direction,
// and up direction in 3d space, corresponding to pixel x,y coordinates of each face
static constexpr std::array<std::array<math::Vec3f, 3>, 6> startRightUp = {{
{{{-1.0f, -1.0f, -1.0f}, { 1.0f, 0.0f, 0.0f}, {0.0f, 1.0f, 0.0f}}}, // front
{{{ 1.0f, -1.0f, 1.0f}, {-1.0f, 0.0f, 0.0f}, {0.0f, 1.0f, 0.0f}}}, // back
{{{-1.0f, -1.0f, 1.0f}, { 0.0f, 0.0f, -1.0f}, {0.0f, 1.0f, 0.0f}}}, // left
{{{ 1.0f, -1.0f, -1.0f}, { 0.0f, 0.0f, 1.0f}, {0.0f, 1.0f, 0.0f}}}, // right
{{{-1.0f, 1.0f, -1.0f}, { 1.0f, 0.0f, 0.0f}, {0.0f, 0.0f, 1.0f}}}, // up
{{{-1.0f, -1.0f, 1.0f}, { 1.0f, 0.0f, 0.0f}, {0.0f, 0.0f, -1.0f}}}, // down
{{{ 1.0f, -1.0f, -1.0f}, { 0.0f, 1.0f, 0.0f}, {-1.0f, 0.0f, 0.0f}}}, // front
{{{ 1.0f, 1.0f, 1.0f}, { 0.0f,-1.0f, 0.0f}, {-1.0f, 0.0f, 0.0f}}}, // back
{{{ 1.0f, 1.0f, 1.0f}, { 0.0f, 0.0f, -1.0f}, { 0.0f,-1.0f, 0.0f}}}, // right
{{{-1.0f, -1.0f, 1.0f}, { 0.0f, 0.0f, -1.0f}, { 0.0f, 1.0f, 0.0f}}}, // left
{{{ 1.0f, -1.0f, 1.0f}, { 0.0f, 0.0f, -1.0f}, {-1.0f, 0.0f, 0.0f}}}, // up
{{{ 1.0f, 1.0f, -1.0f}, { 0.0f, 0.0f, 1.0f}, {-1.0f, 0.0f, 0.0f}}}, // down
}};

std::array<std::vector<std::byte>, 6> faceData;
Expand Down