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/* Swizzle.cpp
Copyright (c) 2025 by Daniel Yoon
Endless Sky is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later version.
Endless Sky is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "Swizzle.h"
#include "Color.h"
#include "DataNode.h"
#include <algorithm>
#include <utility>
using namespace std;
namespace {
constexpr int STRIDE = 4;
}
void Swizzle::Load(const DataNode &node)
{
name = node.Token(1);
for(const DataNode &child : node)
{
const string &key = child.Token(0);
// The corresponding row of the matrix for each channel name.
static const array<pair<string, int>, 4> channels = {{
{"red", 0},
{"green", 1},
{"blue", 2},
{"alpha", 3}
}};
auto channel = find_if(channels.cbegin(), channels.cend(), [key](const auto &kv)
{
return kv.first == key;
});
if(channel != channels.cend())
{
// Fill in the row of the matrix for the channel.
// We subtract one to account for the name being in the node.
int channelStartIndex = channel->second * STRIDE;
int elementNum = min(child.Size() - 1, 4);
for(int i = 0; i < elementNum; i++)
matrix[channelStartIndex + i] = child.Value(i + 1);
}
else if(key == "override")
overrideMask = true;
else
child.PrintTrace("Unrecognized attribute in swizzle definition:");
}
// Special-case flag for when applying a swizzle would do nothing at all.
identity = matrix == IDENTITY_MATRIX;
loaded = true;
}
bool Swizzle::IsLoaded() const
{
return loaded;
}
const string &Swizzle::Name() const
{
return name;
}
bool Swizzle::IsIdentity() const
{
return identity;
}
bool Swizzle::OverrideMask() const
{
return overrideMask;
}
const float *Swizzle::MatrixPtr() const
{
return matrix.data();
}
Color Swizzle::Apply(const Color &to) const
{
const float *colorPtr = to.Get();
array<float, 4> newColor = {0, 0, 0, 0};
// Manual matrix multiply into newColor.
for(int i = 0; i < 4; i++)
for(int j = 0; j < 4; j++)
newColor[i] += colorPtr[j] * matrix[i * STRIDE + j];
return Color(newColor[0], newColor[1], newColor[2], newColor[3]);
}
const Swizzle *Swizzle::None()
{
static const Swizzle IDENTITY_SWIZZLE(
true,
true,
true,
IDENTITY_MATRIX
);
return &IDENTITY_SWIZZLE;
}
Swizzle::Swizzle(bool identity, bool loaded, bool overrideMask, array<float, 16> matrix)
: identity(identity), loaded(loaded), overrideMask(overrideMask), matrix(matrix)
{
}
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