mirror of
https://github.com/wheremyfoodat/Panda3DS.git
synced 2025-04-06 22:25:41 +12:00
116 lines
3.5 KiB
C++
116 lines
3.5 KiB
C++
#include <algorithm>
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#include "colour.hpp"
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#include "renderer_mtl/mtl_texture.hpp"
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#include "renderer_mtl/renderer_mtl.hpp"
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using namespace Helpers;
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namespace Metal {
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static constexpr u32 signExtend3To32(u32 val) {
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return (u32)(s32(val) << 29 >> 29);
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}
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u32 Texture::getTexelETC(bool hasAlpha, u32 u, u32 v, u32 width, std::span<const u8> data) {
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// Pixel offset of the 8x8 tile based on u, v and the width of the texture
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u32 offs = ((u & ~7) * 8) + ((v & ~7) * width);
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if (!hasAlpha) {
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offs >>= 1;
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}
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// In-tile offsets for u/v
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u &= 7;
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v &= 7;
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// ETC1(A4) also subdivide the 8x8 tile to 4 4x4 tiles
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// Each tile is 8 bytes for ETC1, but since ETC1A4 has 4 alpha bits per pixel, that becomes 16 bytes
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const u32 subTileSize = hasAlpha ? 16 : 8;
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const u32 subTileIndex = (u / 4) + 2 * (v / 4); // Which of the 4 subtiles is this texel in?
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// In-subtile offsets for u/v
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u &= 3;
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v &= 3;
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offs += subTileSize * subTileIndex;
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u32 alpha;
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const u64* ptr = reinterpret_cast<const u64*>(data.data() + offs); // Cast to u64*
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if (hasAlpha) {
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// First 64 bits of the 4x4 subtile are alpha data
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const u64 alphaData = *ptr++;
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alpha = Colour::convert4To8Bit((alphaData >> (4 * (u * 4 + v))) & 0xf);
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} else {
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alpha = 0xff; // ETC1 without alpha uses ff for every pixel
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}
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// Next 64 bits of the subtile are colour data
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u64 colourData = *ptr;
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return decodeETC(alpha, u, v, colourData);
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}
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u32 Texture::decodeETC(u32 alpha, u32 u, u32 v, u64 colourData) {
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static constexpr u32 modifiers[8][2] = {
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{2, 8}, {5, 17}, {9, 29}, {13, 42}, {18, 60}, {24, 80}, {33, 106}, {47, 183},
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};
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// Parse colour data for 4x4 block
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const u32 subindices = getBits<0, 16, u32>(colourData);
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const u32 negationFlags = getBits<16, 16, u32>(colourData);
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const bool flip = getBit<32>(colourData);
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const bool diffMode = getBit<33>(colourData);
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// Note: index1 is indeed stored on the higher bits, with index2 in the lower bits
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const u32 tableIndex1 = getBits<37, 3, u32>(colourData);
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const u32 tableIndex2 = getBits<34, 3, u32>(colourData);
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const u32 texelIndex = u * 4 + v; // Index of the texel in the block
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if (flip) std::swap(u, v);
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s32 r, g, b;
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if (diffMode) {
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r = getBits<59, 5, s32>(colourData);
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g = getBits<51, 5, s32>(colourData);
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b = getBits<43, 5, s32>(colourData);
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if (u >= 2) {
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r += signExtend3To32(getBits<56, 3, u32>(colourData));
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g += signExtend3To32(getBits<48, 3, u32>(colourData));
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b += signExtend3To32(getBits<40, 3, u32>(colourData));
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}
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// Expand from 5 to 8 bits per channel
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r = Colour::convert5To8Bit(r);
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g = Colour::convert5To8Bit(g);
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b = Colour::convert5To8Bit(b);
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} else {
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if (u < 2) {
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r = getBits<60, 4, s32>(colourData);
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g = getBits<52, 4, s32>(colourData);
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b = getBits<44, 4, s32>(colourData);
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} else {
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r = getBits<56, 4, s32>(colourData);
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g = getBits<48, 4, s32>(colourData);
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b = getBits<40, 4, s32>(colourData);
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}
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// Expand from 4 to 8 bits per channel
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r = Colour::convert4To8Bit(r);
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g = Colour::convert4To8Bit(g);
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b = Colour::convert4To8Bit(b);
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}
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const u32 index = (u < 2) ? tableIndex1 : tableIndex2;
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s32 modifier = modifiers[index][(subindices >> texelIndex) & 1];
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if (((negationFlags >> texelIndex) & 1) != 0) {
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modifier = -modifier;
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}
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r = std::clamp(r + modifier, 0, 255);
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g = std::clamp(g + modifier, 0, 255);
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b = std::clamp(b + modifier, 0, 255);
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return (alpha << 24) | (u32(b) << 16) | (u32(g) << 8) | u32(r);
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}
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} // namespace Metal
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