1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324
use crate::context::CommandContext;
use crate::version::Api;
use crate::version::Version;
use crate::DrawError;
use crate::gl;
/// Blend effect that the GPU will use for blending.
///
/// Blending happens at the end of the rendering process, when the GPU wants to write the
/// pixels over pixels that already exist in the framebuffer. The blending function allows
/// you to choose how it should merge the two.
///
/// If you want to add transparent objects one over another, use
/// `Blend::alpha_blending()`.
#[derive(Copy, Clone, Debug, PartialEq)]
pub struct Blend {
/// The blending function for color channels.
pub color: BlendingFunction,
/// The blending function for alpha channels.
pub alpha: BlendingFunction,
/// A constant color that can be used in the blending functions.
pub constant_value: (f32, f32, f32, f32),
}
impl Blend {
/// Returns a blend effect to add transparent objects over others.
pub fn alpha_blending() -> Blend {
Blend {
color: BlendingFunction::Addition {
source: LinearBlendingFactor::SourceAlpha,
destination: LinearBlendingFactor::OneMinusSourceAlpha,
},
alpha: BlendingFunction::Addition {
source: LinearBlendingFactor::SourceAlpha,
destination: LinearBlendingFactor::OneMinusSourceAlpha
},
constant_value: (0.0, 0.0, 0.0, 0.0)
}
}
}
impl Default for Blend {
fn default() -> Blend {
Blend {
color: BlendingFunction::AlwaysReplace,
alpha: BlendingFunction::AlwaysReplace,
constant_value: (1.0, 1.0, 1.0, 1.0),
}
}
}
/// Function that the GPU will use for blending.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum BlendingFunction {
/// Simply overwrite the destination pixel with the source pixel.
///
/// The alpha channels are simply ignored. This is the default mode.
///
/// For example writing `(0.5, 0.9, 0.4, 0.2)` over `(0.9, 0.1, 0.4, 0.3)` will
/// result in `(0.5, 0.9, 0.4, 0.2)`.
AlwaysReplace,
/// For each individual component (red, green, blue, and alpha), the minimum value is chosen
/// between the source and the destination.
///
/// For example writing `(0.5, 0.9, 0.4, 0.2)` over `(0.9, 0.1, 0.4, 0.3)` will
/// result in `(0.5, 0.1, 0.4, 0.2)`.
Min,
/// For each individual component (red, green, blue, and alpha), the maximum value is chosen
/// between the source and the destination.
///
/// For example writing `(0.5, 0.9, 0.4, 0.2)` over `(0.9, 0.1, 0.4, 0.3)` will
/// result in `(0.9, 0.9, 0.4, 0.3)`.
Max,
/// For each individual component (red, green, blue, and alpha), a weighted addition
/// between the source and the destination.
///
/// The result is equal to `source_component * source_factor + dest_component * dest_factor`,
/// where `source_factor` and `dest_factor` are the values of `source` and `destination` of
/// this enum.
Addition {
/// The factor to apply to the source pixel.
source: LinearBlendingFactor,
/// The factor to apply to the destination pixel.
destination: LinearBlendingFactor,
},
/// For each individual component (red, green, blue, and alpha), a weighted subtraction
/// of the source by the destination.
///
/// The result is equal to `source_component * source_factor - dest_component * dest_factor`,
/// where `source_factor` and `dest_factor` are the values of `source` and `destination` of
/// this enum.
Subtraction {
/// The factor to apply to the source pixel.
source: LinearBlendingFactor,
/// The factor to apply to the destination pixel.
destination: LinearBlendingFactor,
},
/// For each individual component (red, green, blue, and alpha), a weighted subtraction
/// of the destination by the source.
///
/// The result is equal to `-source_component * source_factor + dest_component * dest_factor`,
/// where `source_factor` and `dest_factor` are the values of `source` and `destination` of
/// this enum.
ReverseSubtraction {
/// The factor to apply to the source pixel.
source: LinearBlendingFactor,
/// The factor to apply to the destination pixel.
destination: LinearBlendingFactor,
},
}
/// Indicates which value to multiply each component with.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum LinearBlendingFactor {
/// Multiply the source or destination component by zero, which always
/// gives `0.0`.
Zero,
/// Multiply the source or destination component by one, which always
/// gives you the original value.
One,
/// Multiply the source or destination component by its corresponding value
/// in the source.
///
/// If you apply this to the source components, you get the values squared.
SourceColor,
/// Equivalent to `1 - SourceColor`.
OneMinusSourceColor,
/// Multiply the source or destination component by its corresponding value
/// in the destination.
///
/// If you apply this to the destination components, you get the values squared.
DestinationColor,
/// Equivalent to `1 - DestinationColor`.
OneMinusDestinationColor,
/// Multiply the source or destination component by the alpha value of the source.
SourceAlpha,
/// Multiply the source or destination component by the smallest value of
/// `SourceAlpha` and `1 - DestinationAlpha`.
SourceAlphaSaturate,
/// Multiply the source or destination component by `1.0` minus the alpha value of the source.
OneMinusSourceAlpha,
/// Multiply the source or destination component by the alpha value of the destination.
DestinationAlpha,
/// Multiply the source or destination component by `1.0` minus the alpha value of the
/// destination.
OneMinusDestinationAlpha,
/// Multiply the source or destination component by the corresponding value
/// in `Blend::const_value`.
ConstantColor,
/// Multiply the source or destination component by `1.0` minus the corresponding
/// value in `Blend::const_value`.
OneMinusConstantColor,
/// Multiply the source or destination component by the alpha value of `Blend::const_value`.
ConstantAlpha,
/// Multiply the source or destination component by `1.0` minus the alpha value of
/// `Blend::const_value`.
OneMinusConstantAlpha,
}
impl LinearBlendingFactor {
fn to_glenum(&self) -> gl::types::GLenum {
match *self {
LinearBlendingFactor::Zero => gl::ZERO,
LinearBlendingFactor::One => gl::ONE,
LinearBlendingFactor::SourceColor => gl::SRC_COLOR,
LinearBlendingFactor::OneMinusSourceColor => gl::ONE_MINUS_SRC_COLOR,
LinearBlendingFactor::DestinationColor => gl::DST_COLOR,
LinearBlendingFactor::OneMinusDestinationColor => gl::ONE_MINUS_DST_COLOR,
LinearBlendingFactor::SourceAlpha => gl::SRC_ALPHA,
LinearBlendingFactor::OneMinusSourceAlpha => gl::ONE_MINUS_SRC_ALPHA,
LinearBlendingFactor::DestinationAlpha => gl::DST_ALPHA,
LinearBlendingFactor::OneMinusDestinationAlpha => gl::ONE_MINUS_DST_ALPHA,
LinearBlendingFactor::SourceAlphaSaturate => gl::SRC_ALPHA_SATURATE,
LinearBlendingFactor::ConstantColor => gl::CONSTANT_COLOR,
LinearBlendingFactor::OneMinusConstantColor => gl::ONE_MINUS_CONSTANT_COLOR,
LinearBlendingFactor::ConstantAlpha => gl::CONSTANT_ALPHA,
LinearBlendingFactor::OneMinusConstantAlpha => gl::ONE_MINUS_CONSTANT_ALPHA,
}
}
}
pub fn sync_blending(ctxt: &mut CommandContext<'_>, blend: Blend) -> Result<(), DrawError> {
#[inline(always)]
fn blend_eq(ctxt: &mut CommandContext<'_>, blending_function: BlendingFunction)
-> Result<gl::types::GLenum, DrawError>
{
match blending_function {
BlendingFunction::AlwaysReplace |
BlendingFunction::Addition { .. } => Ok(gl::FUNC_ADD),
BlendingFunction::Subtraction { .. } => Ok(gl::FUNC_SUBTRACT),
BlendingFunction::ReverseSubtraction { .. } => Ok(gl::FUNC_REVERSE_SUBTRACT),
BlendingFunction::Min => {
if ctxt.version <= &Version(Api::GlEs, 2, 0) &&
!ctxt.extensions.gl_ext_blend_minmax
{
Err(DrawError::BlendingParameterNotSupported)
} else {
Ok(gl::MIN)
}
},
BlendingFunction::Max => {
if ctxt.version <= &Version(Api::GlEs, 2, 0) &&
!ctxt.extensions.gl_ext_blend_minmax
{
Err(DrawError::BlendingParameterNotSupported)
} else {
Ok(gl::MAX)
}
},
}
}
#[inline(always)]
fn blending_factors(blending_function: BlendingFunction)
-> Option<(LinearBlendingFactor, LinearBlendingFactor)>
{
match blending_function {
BlendingFunction::AlwaysReplace |
BlendingFunction::Min |
BlendingFunction::Max => None,
BlendingFunction::Addition { source, destination } =>
Some((source, destination)),
BlendingFunction::Subtraction { source, destination } =>
Some((source, destination)),
BlendingFunction::ReverseSubtraction { source, destination } =>
Some((source, destination)),
}
}
if let (BlendingFunction::AlwaysReplace, BlendingFunction::AlwaysReplace) =
(blend.color, blend.alpha)
{
// Both color and alpha always replace. This equals no blending.
if ctxt.state.enabled_blend {
unsafe { ctxt.gl.Disable(gl::BLEND); }
ctxt.state.enabled_blend = false;
}
} else {
if !ctxt.state.enabled_blend {
unsafe { ctxt.gl.Enable(gl::BLEND); }
ctxt.state.enabled_blend = true;
}
let (color_eq, alpha_eq) = (blend_eq(ctxt, blend.color)?,
blend_eq(ctxt, blend.alpha)?);
if ctxt.state.blend_equation != (color_eq, alpha_eq) {
unsafe { ctxt.gl.BlendEquationSeparate(color_eq, alpha_eq); }
ctxt.state.blend_equation = (color_eq, alpha_eq);
}
// Map to dummy factors if the blending equation does not use the factors.
let (color_factor_src, color_factor_dst) = blending_factors(blend.color)
.unwrap_or((LinearBlendingFactor::One, LinearBlendingFactor::Zero));
let (alpha_factor_src, alpha_factor_dst) = blending_factors(blend.alpha)
.unwrap_or((LinearBlendingFactor::One, LinearBlendingFactor::Zero));
// Updating the blending color if necessary.
if (color_factor_src == LinearBlendingFactor::ConstantColor ||
color_factor_src == LinearBlendingFactor::OneMinusConstantColor ||
color_factor_dst == LinearBlendingFactor::ConstantColor ||
color_factor_dst == LinearBlendingFactor::OneMinusConstantColor ||
alpha_factor_src == LinearBlendingFactor::ConstantColor ||
alpha_factor_src == LinearBlendingFactor::OneMinusConstantColor ||
alpha_factor_dst == LinearBlendingFactor::ConstantColor ||
alpha_factor_dst == LinearBlendingFactor::OneMinusConstantColor ||
color_factor_src == LinearBlendingFactor::ConstantAlpha ||
color_factor_src == LinearBlendingFactor::OneMinusConstantAlpha ||
color_factor_dst == LinearBlendingFactor::ConstantAlpha ||
color_factor_dst == LinearBlendingFactor::OneMinusConstantAlpha ||
alpha_factor_src == LinearBlendingFactor::ConstantAlpha ||
alpha_factor_src == LinearBlendingFactor::OneMinusConstantAlpha ||
alpha_factor_dst == LinearBlendingFactor::ConstantAlpha ||
alpha_factor_dst == LinearBlendingFactor::OneMinusConstantAlpha) && ctxt.state.blend_color != blend.constant_value {
let (r, g, b, a) = blend.constant_value;
unsafe { ctxt.gl.BlendColor(r, g, b, a); }
ctxt.state.blend_color = blend.constant_value;
}
// Updating the blending function if necessary.
let color_factor_src = color_factor_src.to_glenum();
let color_factor_dst = color_factor_dst.to_glenum();
let alpha_factor_src = alpha_factor_src.to_glenum();
let alpha_factor_dst = alpha_factor_dst.to_glenum();
if ctxt.state.blend_func != (color_factor_src, color_factor_dst,
alpha_factor_src, alpha_factor_dst)
{
unsafe {
ctxt.gl.BlendFuncSeparate(color_factor_src, color_factor_dst,
alpha_factor_src, alpha_factor_dst);
}
ctxt.state.blend_func = (color_factor_src, color_factor_dst,
alpha_factor_src, alpha_factor_dst);
}
}
Ok(())
}