105 lines
3.7 KiB
C++
105 lines
3.7 KiB
C++
/*
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* Copyright (C) 2021 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef TNT_GEOMETRY_TRANSCODER_H
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#define TNT_GEOMETRY_TRANSCODER_H
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#include <utils/compiler.h>
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#include <stddef.h>
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#include <stdint.h>
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namespace filament {
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namespace geometry {
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enum class ComponentType {
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BYTE, //!< If normalization is enabled, this maps from [-127,127] to [-1,+1]
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UBYTE, //!< If normalization is enabled, this maps from [0,255] to [0, +1]
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SHORT, //!< If normalization is enabled, this maps from [-32767,32767] to [-1,+1]
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USHORT, //!< If normalization is enabled, this maps from [0,65535] to [0, +1]
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HALF, //!< 1 sign bit, 5 exponent bits, and 5 mantissa bits.
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};
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/**
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* Creates a function object that can convert vertex attribute data into tightly packed floats.
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*
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* This is especially useful for 3-component formats which are not supported by all backends.
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* e.g. The Vulkan minspec includes float3 but not short3.
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*
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* Usage Example:
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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* using filament::geometry::Transcoder;
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* using filament::geometry::ComponentType;
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*
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* Transcoder transcode({
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* .componentType = ComponentType::BYTE,
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* .normalized = true,
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* .componentCount = 3,
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* .inputStrideBytes = 0
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* });
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*
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* transcode(outputPtr, inputPtr, count);
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* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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*
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* The interpretation of signed normalized data is consistent with Vulkan and OpenGL ES 3.0+.
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* Note that this slightly differs from earlier versions of OpenGL ES. For example, a signed byte
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* value of -127 maps exactly to -1.0f under ES3 and VK rules, but not ES2.
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*/
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class UTILS_PUBLIC Transcoder {
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public:
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/**
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* Describes the format of all input data that get passed to this transcoder object.
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*/
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struct Config {
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ComponentType componentType;
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bool normalized;
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uint32_t componentCount;
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uint32_t inputStrideBytes = 0; //!< If stride is 0, the transcoder assumes tight packing.
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};
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/**
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* Creates an immutable function object with the specified configuration.
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*
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* The config is not passed by const reference to allow for type inference at the call site.
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*/
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Transcoder(Config config) noexcept : mConfig(config) {}
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/**
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* Converts arbitrary data into tightly packed 32-bit floating point values.
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*
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* If target is non-null, writes up to "count" items into target and returns the number of bytes
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* actually written.
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*
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* If target is null, returns the number of bytes required.
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*
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* @param target Client owned area to write into, or null for a size query
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* @param source Pointer to the data to read from (does not get retained)
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* @param count The maximum number of items to write (i.e. number of float3 values, not bytes)
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* @return Number of bytes required to contain "count" items after conversion to packed floats
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*
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*/
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size_t operator()(float* UTILS_RESTRICT target, void const* UTILS_RESTRICT source,
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size_t count) const noexcept;
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private:
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const Config mConfig;
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};
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} // namespace geometry
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} // namespace filament
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#endif // TNT_GEOMETRY_TRANSCODER_H
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