Panda3DS/src/core/renderer_mtl/mtl_texture.cpp

#include "renderer_mtl/mtl_texture.hpp"
#include "renderer_mtl/objc_helper.hpp"
#include "colour.hpp"
#include <array>

using namespace Helpers;

namespace Metal {

void Texture::allocate() {
    formatInfo = PICA::getPixelFormatInfo(format);

    MTL::TextureDescriptor* descriptor = MTL::TextureDescriptor::alloc()->init();
    descriptor->setTextureType(MTL::TextureType2D);
    descriptor->setPixelFormat(formatInfo.pixelFormat);
    descriptor->setWidth(size.u());
    descriptor->setHeight(size.v());
    descriptor->setUsage(MTL::TextureUsageShaderRead);
    descriptor->setStorageMode(MTL::StorageModeShared); // TODO: use private + staging buffers?
    texture = device->newTexture(descriptor);
    texture->setLabel(toNSString("Texture " + std::string(PICA::textureFormatToString(format)) + " " + std::to_string(size.u()) + "x" + std::to_string(size.v())));
    descriptor->release();

    setNewConfig(config);
}

// Set the texture's configuration, which includes min/mag filters, wrapping S/T modes, and so on
void Texture::setNewConfig(u32 cfg) {
    config = cfg;

    if (sampler) {
        sampler->release();
    }

    const auto magFilter = (cfg & 0x2) != 0 ? MTL::SamplerMinMagFilterLinear : MTL::SamplerMinMagFilterNearest;
    const auto minFilter = (cfg & 0x4) != 0 ? MTL::SamplerMinMagFilterLinear : MTL::SamplerMinMagFilterNearest;
    const auto wrapT = PICA::toMTLSamplerAddressMode(getBits<8, 3>(cfg));
    const auto wrapS = PICA::toMTLSamplerAddressMode(getBits<12, 3>(cfg));

    MTL::SamplerDescriptor* samplerDescriptor = MTL::SamplerDescriptor::alloc()->init();
    samplerDescriptor->setMinFilter(minFilter);
    samplerDescriptor->setMagFilter(magFilter);
    samplerDescriptor->setSAddressMode(wrapS);
    samplerDescriptor->setTAddressMode(wrapT);

    samplerDescriptor->setLabel(toNSString("Sampler"));
    sampler = device->newSamplerState(samplerDescriptor);
    samplerDescriptor->release();
}

void Texture::free() {
	valid = false;

	if (texture) {
		texture->release();
	}
	if (sampler) {
        sampler->release();
    }
}

u64 Texture::sizeInBytes() {
    u64 pixelCount = u64(size.x()) * u64(size.y());

    switch (format) {
    case PICA::TextureFmt::RGBA8: // 4 bytes per pixel
        return pixelCount * 4;

    case PICA::TextureFmt::RGB8: // 3 bytes per pixel
        return pixelCount * 3;

    case PICA::TextureFmt::RGBA5551: // 2 bytes per pixel
    case PICA::TextureFmt::RGB565:
    case PICA::TextureFmt::RGBA4:
    case PICA::TextureFmt::RG8:
    case PICA::TextureFmt::IA8:
        return pixelCount * 2;

    case PICA::TextureFmt::A8: // 1 byte per pixel
    case PICA::TextureFmt::I8:
    case PICA::TextureFmt::IA4:
        return pixelCount;

    case PICA::TextureFmt::I4: // 4 bits per pixel
    case PICA::TextureFmt::A4:
        return pixelCount / 2;

    case PICA::TextureFmt::ETC1: // Compressed formats
    case PICA::TextureFmt::ETC1A4: {
        // Number of 4x4 tiles
        const u64 tileCount = pixelCount / 16;
        // Tiles are 8 bytes each on ETC1 and 16 bytes each on ETC1A4
        const u64 tileSize = format == PICA::TextureFmt::ETC1 ? 8 : 16;
        return tileCount * tileSize;
    }

    default:
        Helpers::panic("[PICA] Attempted to get size of invalid texture type");
    }
}

// u and v are the UVs of the relevant texel
// Texture data is stored interleaved in Morton order, ie in a Z - order curve as shown here
// https://en.wikipedia.org/wiki/Z-order_curve
// Textures are split into 8x8 tiles.This function returns the in - tile offset depending on the u & v of the texel
// The in - tile offset is the sum of 2 offsets, one depending on the value of u % 8 and the other on the value of y % 8
// As documented in this picture https ://en.wikipedia.org/wiki/File:Moser%E2%80%93de_Bruijn_addition.svg
u32 Texture::mortonInterleave(u32 u, u32 v) {
    static constexpr u32 xOffsets[] = { 0, 1, 4, 5, 16, 17, 20, 21 };
    static constexpr u32 yOffsets[] = { 0, 2, 8, 10, 32, 34, 40, 42 };

    return xOffsets[u & 7] + yOffsets[v & 7];
}

// Get the byte offset of texel (u, v) in the texture
u32 Texture::getSwizzledOffset(u32 u, u32 v, u32 width, u32 bytesPerPixel) {
    u32 offset = ((u & ~7) * 8) + ((v & ~7) * width); // Offset of the 8x8 tile the texel belongs to
    offset += mortonInterleave(u, v); // Add the in-tile offset of the texel

    return offset * bytesPerPixel;
}

// Same as the above code except we need to divide by 2 because 4 bits is smaller than a byte
u32 Texture::getSwizzledOffset_4bpp(u32 u, u32 v, u32 width) {
    u32 offset = ((u & ~7) * 8) + ((v & ~7) * width); // Offset of the 8x8 tile the texel belongs to
    offset += mortonInterleave(u, v); // Add the in-tile offset of the texel

    return offset / 2;
}

u8 Texture::decodeTexelU8(u32 u, u32 v, PICA::TextureFmt fmt, std::span<const u8> data) {
    switch (fmt) {
        case PICA::TextureFmt::A4: {
            const u32 offset = getSwizzledOffset_4bpp(u, v, size.u());

            // For odd U coordinates, grab the top 4 bits, and the low 4 bits for even coordinates
            u8 alpha = data[offset] >> ((u % 2) ? 4 : 0);
            alpha = Colour::convert4To8Bit(getBits<0, 4>(alpha));

            // A8
            return alpha;
        }

        case PICA::TextureFmt::A8: {
            u32 offset = getSwizzledOffset(u, v, size.u(), 1);
            const u8 alpha = data[offset];

            // A8
            return alpha;
        }

        default:
            Helpers::panic("[Texture::DecodeTexel] Unimplemented format = %d", static_cast<int>(fmt));
    }
}

u16 Texture::decodeTexelU16(u32 u, u32 v, PICA::TextureFmt fmt, std::span<const u8> data) {
    switch (fmt) {
        case PICA::TextureFmt::RG8: {
            u32 offset = getSwizzledOffset(u, v, size.u(), 2);
            constexpr u8 b = 0;
            const u8 g = data[offset];
            const u8 r = data[offset + 1];

            // RG8
            return (g << 8) | r;
        }

        case PICA::TextureFmt::RGBA4: {
            u32 offset = getSwizzledOffset(u, v, size.u(), 2);
            u16 texel = u16(data[offset]) | (u16(data[offset + 1]) << 8);

            u8 alpha = getBits<0, 4, u8>(texel);
            u8 b = getBits<4, 4, u8>(texel);
            u8 g = getBits<8, 4, u8>(texel);
            u8 r = getBits<12, 4, u8>(texel);

            // ABGR4
            return (r << 12) | (g << 8) | (b << 4) | alpha;
        }

        case PICA::TextureFmt::RGBA5551: {
            const u32 offset = getSwizzledOffset(u, v, size.u(), 2);
            const u16 texel = u16(data[offset]) | (u16(data[offset + 1]) << 8);

            u8 alpha = getBit<0>(texel) ? 0xff : 0;
            u8 b = getBits<1, 5, u8>(texel);
            u8 g = getBits<6, 5, u8>(texel);
            u8 r = getBits<11, 5, u8>(texel);

            // BGR5A1
            return (alpha << 15) | (r << 10) | (g << 5) | b;
        }

        case PICA::TextureFmt::RGB565: {
            const u32 offset = getSwizzledOffset(u, v, size.u(), 2);
            const u16 texel = u16(data[offset]) | (u16(data[offset + 1]) << 8);

            const u8 b = getBits<0, 5, u8>(texel);
            const u8 g = getBits<5, 6, u8>(texel);
            const u8 r = getBits<11, 5, u8>(texel);

            // B5G6R5
            return (r << 11) | (g << 5) | b;
        }

        case PICA::TextureFmt::IA4: {
            const u32 offset = getSwizzledOffset(u, v, size.u(), 1);
            const u8 texel = data[offset];
            const u8 alpha = texel & 0xf;
            const u8 intensity = texel >> 4;

            // ABGR4
            return (intensity << 12) | (intensity << 8) | (intensity << 4) | alpha;
        }

        case PICA::TextureFmt::I4: {
            u32 offset = getSwizzledOffset_4bpp(u, v, size.u());

            // For odd U coordinates, grab the top 4 bits, and the low 4 bits for even coordinates
            u8 intensity = data[offset] >> ((u % 2) ? 4 : 0);
            intensity = getBits<0, 4>(intensity);

            // ABGR4
            return (intensity << 12) | (intensity << 8) | (intensity << 4) | 0xff;
        }

        default:
            Helpers::panic("[Texture::DecodeTexel] Unimplemented format = %d", static_cast<int>(fmt));
    }
}

u32 Texture::decodeTexelU32(u32 u, u32 v, PICA::TextureFmt fmt, std::span<const u8> data) {
    switch (fmt) {
        case PICA::TextureFmt::RGB8: {
            const u32 offset = getSwizzledOffset(u, v, size.u(), 3);
            const u8 b = data[offset];
            const u8 g = data[offset + 1];
            const u8 r = data[offset + 2];

            // RGBA8
            return (0xff << 24) | (b << 16) | (g << 8) | r;
        }

        case PICA::TextureFmt::RGBA8: {
            const u32 offset = getSwizzledOffset(u, v, size.u(), 4);
            const u8 alpha = data[offset];
            const u8 b = data[offset + 1];
            const u8 g = data[offset + 2];
            const u8 r = data[offset + 3];

            // RGBA8
            return (alpha << 24) | (b << 16) | (g << 8) | r;
        }

        case PICA::TextureFmt::I8: {
            u32 offset = getSwizzledOffset(u, v, size.u(), 1);
            const u8 intensity = data[offset];

            // RGBA8
            return (0xff << 24) | (intensity << 16) | (intensity << 8) | intensity;
        }

        case PICA::TextureFmt::IA8: {
            u32 offset = getSwizzledOffset(u, v, size.u(), 2);

            // Same as I8 except each pixel gets its own alpha value too
            const u8 alpha = data[offset];
            const u8 intensity = data[offset + 1];

            // RGBA8
            return (alpha << 24) | (intensity << 16) | (intensity << 8) | intensity;
        }

        case PICA::TextureFmt::ETC1: return getTexelETC(false, u, v, size.u(), data);
        case PICA::TextureFmt::ETC1A4: return getTexelETC(true, u, v, size.u(), data);

        default:
            Helpers::panic("[Texture::DecodeTexel] Unimplemented format = %d", static_cast<int>(fmt));
    }
}

void Texture::decodeTexture(std::span<const u8> data) {
    std::vector<u8> decoded;
    decoded.reserve(u64(size.u()) * u64(size.v()) * formatInfo.bytesPerTexel);

    // Decode texels line by line
    for (u32 v = 0; v < size.v(); v++) {
        for (u32 u = 0; u < size.u(); u++) {
            if (formatInfo.bytesPerTexel == 1) {
                u8 texel = decodeTexelU8(u, v, format, data);
                decoded.push_back(texel);
            } else if (formatInfo.bytesPerTexel == 2) {
                u16 texel = decodeTexelU16(u, v, format, data);
                decoded.push_back((texel & 0x00ff) >> 0);
                decoded.push_back((texel & 0xff00) >> 8);
            } else if (formatInfo.bytesPerTexel == 4) {
                u32 texel = decodeTexelU32(u, v, format, data);
                decoded.push_back((texel & 0x000000ff) >> 0);
                decoded.push_back((texel & 0x0000ff00) >> 8);
                decoded.push_back((texel & 0x00ff0000) >> 16);
                decoded.push_back((texel & 0xff000000) >> 24);
            } else {
                Helpers::panic("[Texture::decodeTexture] Unimplemented bytesPerTexel (%u)", formatInfo.bytesPerTexel);
            }
        }
    }

    texture->replaceRegion(MTL::Region(0, 0, size.u(), size.v()), 0, 0, decoded.data(), formatInfo.bytesPerTexel * size.u(), 0);
}

} // namespace Metal