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Improve texture atlas handling

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Avoid the manual padding of images in the texture atlas. This is a
CPU-side expensive operation and we can avoid doing that by instead
adjusting the texture coordinates to map to the center of the texels.
This is also described nicely in
https://docs.microsoft.com/en-us/windows/win32/direct3d9/directly-mapping-texels-to-pixels
This commit is contained in:
Simon Hausmann 2020-10-01 09:50:59 +02:00
parent 7e0e7b43f0
commit fdebd8427d
1 changed files with 7 additions and 67 deletions
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74
sixtyfps_runtime/rendering_backends/gl/texture.rs
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@ -150,7 +150,7 @@ pub(crate) struct GLAtlasTexture {
} }
pub struct AtlasAllocation { pub struct AtlasAllocation {
pub texture_coordinates: RectI, // excludes padding pub texture_coordinates: RectI,
allocation_id: guillotiere::AllocId, allocation_id: guillotiere::AllocId,
pub(crate) atlas: Rc<GLAtlasTexture>, pub(crate) atlas: Rc<GLAtlasTexture>,
} }
@ -169,10 +169,10 @@ impl AtlasAllocation {
let size = self.texture_coordinates.size(); let size = self.texture_coordinates.size();
let texture_coordinates = RectI::new(origin, size); let texture_coordinates = RectI::new(origin, size);
let tex_left = (texture_coordinates.min_x() as f32) / atlas_width; let tex_left = ((texture_coordinates.min_x() as f32) + 0.5) / atlas_width;
let tex_top = (texture_coordinates.min_y() as f32) / atlas_height; let tex_top = ((texture_coordinates.min_y() as f32) + 0.5) / atlas_height;
let tex_right = (texture_coordinates.max_x() as f32) / atlas_width; let tex_right = ((texture_coordinates.max_x() as f32) - 0.5) / atlas_width;
let tex_bottom = (texture_coordinates.max_y() as f32) / atlas_height; let tex_bottom = ((texture_coordinates.max_y() as f32) - 0.5) / atlas_height;
let tex_vertex1 = Vertex { _pos: [tex_left, tex_top] }; let tex_vertex1 = Vertex { _pos: [tex_left, tex_top] };
let tex_vertex2 = Vertex { _pos: [tex_right, tex_top] }; let tex_vertex2 = Vertex { _pos: [tex_right, tex_top] };
@ -251,74 +251,14 @@ impl TextureAtlas {
gl: &Rc<glow::Context>, gl: &Rc<glow::Context>,
image: image::ImageBuffer<image::Rgba<u8>, &[u8]>, image: image::ImageBuffer<image::Rgba<u8>, &[u8]>,
) -> AtlasAllocation { ) -> AtlasAllocation {
use image::GenericImage; let allocation = self.allocate_region(gl, image.width() as _, image.height() as _);
use image::GenericImageView;
// To avoid pixels leaking from adjacent textures in the atlas when scaling, add a one-pixel
// padding.
let requested_width = image.width() + 2;
let requested_height = image.height() + 2;
let mut padded_image = image::ImageBuffer::new(requested_width, requested_height);
let mut blit = |target_x, target_y, source_x, source_y, source_width, source_height| {
padded_image
.copy_from(
&image.view(source_x, source_y, source_width, source_height),
target_x,
target_y,
)
.ok()
.unwrap();
};
// First the main image itself
blit(1, 1, 0, 0, image.width(), image.height());
// duplicate the top edge
blit(1, 0, 0, 0, image.width(), 1);
// duplicate the bottom edge
blit(1, requested_height - 1, 0, image.height() - 1, image.width(), 1);
// duplicate the left edge
blit(0, 1, 0, 0, 1, image.height());
// duplicate the right edge
blit(requested_width - 1, 1, image.width() - 1, 0, 1, image.height());
// duplicate the top-left corner pixel
blit(0, 0, 0, 0, 1, 1);
// duplicate the bottom-left corner pixel
blit(0, requested_height - 1, 0, image.height() - 1, 1, 1);
// duplicate the top-right corner pixel
blit(requested_width - 1, 0, image.width() - 1, 0, 1, 1);
// duplicate the bottom-right corner pixel
blit(
requested_width - 1,
requested_height - 1,
image.width() - 1,
image.height() - 1,
1,
1,
);
let mut allocation = self.allocate_region(gl, requested_width as _, requested_height as _);
allocation.atlas.texture.set_sub_image( allocation.atlas.texture.set_sub_image(
allocation.texture_coordinates.origin_x(), allocation.texture_coordinates.origin_x(),
allocation.texture_coordinates.origin_y(), allocation.texture_coordinates.origin_y(),
padded_image, image,
); );
// Remove the padding from the coordinates we use for sampling
allocation.texture_coordinates =
allocation.texture_coordinates.contract(Vector2I::new(1, 1));
allocation allocation
} }
} }