| // |
| // Copyright 2019 The ANGLE Project Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| // |
| // ConvertIndex.comp: Convert UINT_8 indices into UINT_16 using a compute shader. |
| // |
| // The following defines tweak the functionality, and a different shader is built based on these. |
| // |
| // - Flags: |
| // * IsPrimitiveRestartEnabled: enables conversion from 0xFF to 0xFFFF, |
| // the restart indices for 8-bit and 16-bit indices. |
| // |
| |
| #version 450 core |
| |
| layout (local_size_x = 64, local_size_y = 1, local_size_z = 1) in; |
| |
| layout (set = 0, binding = 0) buffer dst |
| { |
| // Shader invocations output one packed 32-bit value with up to two 16-bit indices. |
| uint dstData[]; |
| }; |
| |
| layout (set = 0, binding = 1) readonly buffer src |
| { |
| // Shader invocations read at most 16 bits of one packed 32-bit value. (Two 8-bit indices.) |
| uint srcData[]; |
| }; |
| |
| layout (push_constant) uniform PushConstants |
| { |
| // Read offset in bytes into the srcData array. |
| uint srcOffset; |
| // Write offset in bytes into the dstData array, divided by four. |
| uint dstOffsetDiv4; |
| // Maximum size of the read buffer. The highest index value we will convert. |
| uint maxIndex; |
| // Not used in the shader. Kept to pad "PushConstants" to the size of a vec4. |
| uint _padding; |
| }; |
| |
| uint PullIndex(uint index) |
| { |
| uint srcIndex = index + srcOffset; |
| uint srcBlock = srcData[srcIndex >> 2]; |
| uint srcComponent = (srcIndex & 3); |
| |
| uint value = (srcBlock >> (srcComponent << 3)) & 0xFF; |
| #if IsPrimitiveRestartEnabled |
| // convert 0xFF (restart value for 8-bit indices) |
| // to 0xFFFF (restart value for 16-bit indices). |
| if (value == 0xFF) |
| value = 0xFFFF; |
| #endif |
| return value; |
| } |
| |
| void PackIndexValue(uint srcValue, uint indexIndex, inout uint dstValue) |
| { |
| // Pack 16-byte index into the 32-byte destination. |
| dstValue |= srcValue << (indexIndex << 4); |
| } |
| |
| void main() |
| { |
| // The element index is simply the invocation ID times two. |
| uint index = (gl_GlobalInvocationID.x << 1); |
| |
| // Don't write anything to dest if we're entirely past the end of the buffer. |
| // We assume buffer size is uint-aligned. |
| if (index >= maxIndex) |
| return; |
| |
| uint dstValue = 0; |
| |
| uint srcValue = PullIndex(index); |
| PackIndexValue(srcValue, 0, dstValue); |
| |
| // Skip packing the second index if we're after the last element. |
| if (index + 1 < maxIndex) |
| { |
| uint srcValue = PullIndex(index + 1); |
| PackIndexValue(srcValue, 1, dstValue); |
| } |
| |
| dstData[dstOffsetDiv4 + gl_GlobalInvocationID.x] = dstValue; |
| } |