Struct GlFramebuffer

Source

pub struct GlFramebuffer { /* private fields */ }

Expand description

A framebuffer: a color attachment texture plus an optional depth (and stencil) renderbuffer.

The color attachment is always a GlTexture rather than a renderbuffer, so the result can be sampled by a later pass or read back without a resolve blit.

Implementations§

Source §

impl GlFramebuffer

Implements framebuffer assembly, completeness checking, and rebinding.

§Performance

The stored dimensions are what make a rebind after a window resize cheap: a caller can compare the requested size against the stored one and skip the whole re-assembly when they still agree, so binding a framebuffer once per frame costs one bindFramebuffer and two integer comparisons.

Source

pub fn create( context: &WebGl2RenderingContext, width: u32, height: u32, color_format: GpuTextureFormat, depth_format: Option<GpuTextureFormat>, ) -> Option<GlFramebuffer>

Allocates a framebuffer with a color texture and, when depth is Some, a depth renderbuffer of the same size.

The color attachment is always a GlTexture, never a renderbuffer, so the rendered result can be sampled by a later pass or read back without a resolve blit. The depth attachment is a renderbuffer, which is cheaper than a depth texture and is correct for a depth buffer that is written and tested but never sampled.

§Arguments

&WebGl2RenderingContext - The context to allocate against.
u32 - The width in pixels.
u32 - The height in pixels.
GpuTextureFormat - The color attachment’s format.
Option<GpuTextureFormat> - The depth renderbuffer’s format, or None for a color-only target.

§Returns

Option<GlFramebuffer> - The assembled framebuffer, or None when the driver refused to allocate one of its parts.

Source

pub fn bind(&self, context: &WebGl2RenderingContext) -> GlFramebufferStatus

Binds the framebuffer as both the draw and read target, and checks that it is complete.

Binding both targets is deliberate: WebGL 2 separates DRAW_FRAMEBUFFER from READ_FRAMEBUFFER, and a framebuffer bound to only one of them makes a later readPixels silently return the default framebuffer’s contents instead. The status check is what turns a driver-side FRAMEBUFFER_INCOMPLETE_*, which otherwise shows up as a frame that renders nothing at all, into a value the caller can react to.

§Arguments

&WebGl2RenderingContext - The context to bind against.

§Returns

GlFramebufferStatus - Whether the framebuffer is renderable.

Source

pub fn matches(&self, width: u32, height: u32) -> bool

Reports whether the stored attachments still match width by height.

The cheap half of a resize check: a caller that compares this before GlFramebuffer::create can skip re-allocating every attachment just to rebind an unchanged render target once per frame.

§Arguments

u32 - The width to test against.
u32 - The height to test against.

§Returns

bool - true when the attachments already match.

Source

pub fn delete(&mut self, context: &WebGl2RenderingContext)

Releases the framebuffer and its depth renderbuffer.

The color texture is deliberately left alone: it is a GlTexture the caller also owns, and a render target whose contents are about to be sampled must outlive its framebuffer.