Struct Scene

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pub struct Scene { /* private fields */ }

Expand description

The main datatype for rendering graphics.

A Scene stores a sequence of drawing commands, their context, and the associated resources, which can later be rendered.

Most users will render this using Renderer::render_to_texture.

Rendering from a Scene will not clear it, which should be done in a separate step, by calling Scene::reset.

If this is not done for a scene which is retained (to avoid allocations) between frames, this will likely quickly increase the complexity of the render result, leading to crashes or potential host system instability.

Implementations§

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impl Scene

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pub fn new() -> Self

Creates a new scene.

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pub fn reset(&mut self)

Removes all content from the scene.

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pub fn bump_estimate(&self, transform: Option<Affine>) -> BumpAllocatorMemory

Available on crate feature bump_estimate only.

Tally up the bump allocator estimate for the current state of the encoding, taking into account an optional transform applied to the entire scene.

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pub fn encoding(&self) -> &Encoding

Returns the underlying raw encoding.

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pub fn encoding_mut(&mut self) -> &mut Encoding

Returns a mutable reference to the underlying raw encoding.

This can be used to more easily create invalid scenes, and so should be used with care.

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pub fn push_layer( &mut self, blend: impl Into<BlendMode>, alpha: f32, transform: Affine, clip: &impl Shape, )

Pushes a new layer clipped by the specified shape and composed with previous layers using the specified blend mode.

Every drawing command after this call will be clipped by the shape until the layer is popped. For layers which are only added for clipping, you should use push_clip_layer instead.

However, the transforms are not saved or modified by the layer stack. That is, the transform argument to this function only applies a transform to the clip shape.

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pub fn push_luminance_mask_layer( &mut self, alpha: f32, transform: Affine, clip: &impl Shape, )

Pushes a new layer clipped by the specified shape and treated like a luminance mask for the current layer.

That is, content drawn between this and the matching pop_layer call will serve as a luminance mask for the prior content in this layer.

Every drawing command after this call will be clipped by the shape until the layer is popped.

However, the transforms are not saved or modified by the layer stack. That is, the transform argument to this function only applies a transform to the clip shape.

§Transparency and premultiplication

In the current version of Vello, this can lead to some unexpected behaviour when it is used to draw directly onto a render target which disregards transparency (which includes surfaces in most cases). This happens because the luminance mask only impacts the transparency of the returned value, so if the transparency is ignored, it looks like the result had no effect.

This issue only occurs if there are no intermediate opaque layers, so can be worked around by drawing something opaque (or having an opaque base_color), then putting a layer around your entire scene with a Compose::SrcOver.

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pub fn push_clip_layer(&mut self, transform: Affine, clip: &impl Shape)

Pushes a new layer clipped by the specified clip shape.

The pushed layer is intended to not impact the “source” for blending; that is, any blends within this layer will still include content from before this method was called in the “source” of that blend operation. Note that this is not currently implemented correctly - see #1198. As such, you should currently not include any blend layers until this layer is popped.

Every drawing command after this call will be clipped by the shape until the layer is popped.

However, the transforms are not saved or modified by the layer stack. That is, the transform argument to this function only applies a transform to the clip shape.

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pub fn pop_layer(&mut self)

Pops the current layer.

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pub fn draw_blurred_rounded_rect( &mut self, transform: Affine, rect: Rect, brush: Color, radius: f64, std_dev: f64, )

Draw a rounded rectangle blurred with a gaussian filter.

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pub fn draw_blurred_rounded_rect_in( &mut self, shape: &impl Shape, transform: Affine, rect: Rect, brush: Color, radius: f64, std_dev: f64, )

Draw a rounded rectangle blurred with a gaussian filter in shape.

For performance reasons, shape should not extend more than approximately 2.5 times std_dev away from the edges of rect (as any such points will not be perceptably painted to, but calculations will still be performed for them).

This method effectively draws the blurred rounded rectangle clipped to the given shape. If just the blurred rounded rectangle is desired without clipping, use the simpler Self::draw_blurred_rounded_rect. For many users, that method will be easier to use.

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