Struct rerun::external::re_renderer::view_builder::ViewBuilder

pub struct ViewBuilder {
    setup: ViewTargetSetup,
    queued_draws: Vec<QueueableDrawData>,
    outline_mask_processor: Option<OutlineMaskProcessor>,
    screenshot_processor: Option<ScreenshotProcessor>,
    picking_processor: Option<PickingLayerProcessor>,
}

The highest level rendering block in re_renderer. Used to build up/collect various resources and then send them off for rendering of a single view.

Fields

setup: ViewTargetSetup

queued_draws: Vec<QueueableDrawData>

outline_mask_processor: Option<OutlineMaskProcessor>

screenshot_processor: Option<ScreenshotProcessor>

picking_processor: Option<PickingLayerProcessor>

Implementations

impl ViewBuilder

pub const MAIN_TARGET_COLOR_FORMAT: TextureFormat = wgpu::TextureFormat::Rgba8UnormSrgb

Color format used for the main target of the view builder.

Eventually we’ll want to make this an HDR format and apply tonemapping during composite. However, note that it is easy to run into subtle MSAA quality issues then: Applying MSAA resolve before tonemapping is problematic as it means we’re doing msaa in linear. This is especially problematic at bright/dark edges where we may loose “smoothness”! For a nice illustration see this blog post by MRP We either would need to keep the MSAA target and tonemap it, or apply a manual resolve where we inverse-tonemap non-fully-covered pixel before averaging. (an optimized variant of this is described by AMD here) In any case, this gets us onto a potentially much costlier rendering path, especially for tiling GPUs.

pub const MAIN_TARGET_ALPHA_TO_COVERAGE_COLOR_STATE: ColorTargetState = _

Use this color state when targeting the main target with alpha-to-coverage.

If blending with the background is enabled, we need alpha to indicate how much we overwrite the background. (i.e. when we do blending of the screen target with whatever was there during Self::composite.) However, when using alpha-to-coverage, we need alpha to also indicate the coverage of the pixel from which the samples are derived. What we’d like to happen is:

• use alpha to indicate coverage == number of samples written to
• write alpha==1.0 for each active sample despite what we set earlier This way, we’d get the correct alpha and end up with pre-multipltiplied color values during MSAA resolve, just like with opaque geometry! OpenGL exposes this as GL_SAMPLE_ALPHA_TO_ONE, Vulkan as alphaToOne. Unfortunately though, WebGPU does not support this! Instead, what happens is that alpha has a double meaning: Coverage and alpha of all written samples. This means that anti-aliased edges (== alpha < 1.0) will always creates “holes” into the target texture even if there was already an opaque object prior. To work around this, we accumulate alpha values with an additive blending operation, so that previous opaque objects won’t be overwritten with alpha < 1.0. (this is obviously wrong for a variety of reasons, but it looks good enough) Another problem with this is that during MSAA resolve we now average those too low alpha values. This makes us end up with a premultiplied alpha value that looks like it has additive blending applied since the resulting alpha value is not what was used to determine the color! -> See workaround in composite.wgsl

Ultimately, we have the following options to fix this properly sorted from most desirable to least:

• don’t use alpha-to-coverage, use instead SampleMask
  • this is not supported on WebGL which either needs a special path, or more likely, has to just disable anti-aliasing in these cases
  • as long as we use 4x MSAA, we have a pretty good idea where the samples are (see jumpflooding_init_msaa.wgsl), so we can actually use this to improve the quality of the anti-aliasing a lot by turning on/off the samples that are actually covered.
• figure out a way to never needing to blend with the background in Self::composite.
• figure out how to use GL_SAMPLE_ALPHA_TO_ONE after all. This involves bringing this up with the WebGPU spec team and won’t work on WebGL.

pub const SCREENSHOT_COLOR_FORMAT: TextureFormat = wgpu::TextureFormat::Rgba8Unorm

The texture format used for screenshots.

pub const MAIN_TARGET_DEPTH_FORMAT: TextureFormat = wgpu::TextureFormat::Depth32Float

Depth format used for the main target of the view builder.

wgpu::TextureFormat::Depth24Plus would be preferable for performance, see Nvidia’s Vulkan dos and don’ts. However, the problem with being “24Plus” is that we no longer know what format we’ll actually get, which is a problem e.g. for vertex shader determined depth offsets. (This is a real concern - for example on Metal we always get a floating point target with this!) wgpu::TextureFormat::Depth32Float on the other hand is widely supported and has the best possible precision (with reverse infinite z projection which we’re already using).

pub const MAIN_TARGET_SAMPLE_COUNT: u32 = 4u32

Enable MSAA always. This makes our pipeline less variable as well, as we need MSAA resolve steps if we want any MSAA at all!

4 samples are the only thing WebGPU supports, and currently wgpu as well (tracking issue for more options on native)

pub const MAIN_TARGET_DEFAULT_MSAA_STATE: MultisampleState = _

Default multisample state that any wgpu::RenderPipeline drawing to the main target needs to use.

In rare cases, pipelines may want to enable alpha to coverage and/or sample masks.

pub const DEFAULT_DEPTH_CLEAR: LoadOp<f32> = _

Default value for clearing depth buffer to infinity.

0.0 == far since we’re using reverse-z.

pub const MAIN_TARGET_DEFAULT_DEPTH_STATE: Option<DepthStencilState> = _

Default depth state for enabled depth write & read.

pub fn new(ctx: &RenderContext, config: TargetConfiguration) -> ViewBuilder

pub fn resolution_in_pixel(&self) -> [u32; 2]

Resolution in pixels as configured on view builder creation.

pub fn queue_draw( &mut self, draw_data: impl Into<QueueableDrawData> ) -> &mut ViewBuilder

pub fn draw( &self, ctx: &RenderContext, clear_color: Rgba ) -> Result<CommandBuffer, PoolError>

Draws the frame as instructed to a temporary HDR target.

pub fn schedule_screenshot<T>( &mut self, ctx: &RenderContext, identifier: u64, user_data: T ) -> Result<(), ViewBuilderError>

where T: 'static + Send + Sync,

Schedules the taking of a screenshot.

Needs to be called before ViewBuilder::draw. Can only be called once per frame per ViewBuilder.

Data from the screenshot needs to be retrieved via crate::ScreenshotProcessor::next_readback_result. To do so, you need to pass the exact same identifier and type of user data as you’ve done here:

use re_renderer::{view_builder::ViewBuilder, RenderContext, ScreenshotProcessor};
fn take_screenshot(ctx: &RenderContext, view_builder: &mut ViewBuilder) {
    view_builder.schedule_screenshot(&ctx, 42, "My screenshot".to_owned());
}
fn receive_screenshots(ctx: &RenderContext) {
    while ScreenshotProcessor::next_readback_result::<String>(ctx, 42, |data, extent, user_data| {
            re_log::info!("Received screenshot {}", user_data);
        },
    ).is_some()
    {}
}

Received data that isn’t retrieved for more than a frame will be automatically discarded.

pub fn schedule_picking_rect<T>( &mut self, ctx: &RenderContext, picking_rect: RectInt, readback_identifier: u64, readback_user_data: T, show_debug_view: bool ) -> Result<(), ViewBuilderError>

where T: 'static + Send + Sync,

Schedules the readback of a rectangle from the picking layer.

Needs to be called before ViewBuilder::draw. Can only be called once per frame per ViewBuilder.

The result will still be valid if the rectangle is partially or fully outside of bounds. Areas that are not overlapping with the primary target will be filled as-if the view’s target was bigger, i.e. all values are valid picking IDs, it is up to the user to discard anything that is out of bounds.

Note that the picking layer will not be created in the first place if this isn’t called.

Data from the picking rect needs to be retrieved via crate::PickingLayerProcessor::next_readback_result. To do so, you need to pass the exact same identifier and type of user data as you’ve done here:

use re_renderer::{view_builder::ViewBuilder, RectInt, PickingLayerProcessor, RenderContext};
fn schedule_picking_readback(
    ctx: &RenderContext,
    view_builder: &mut ViewBuilder,
    picking_rect: RectInt,
) {
    view_builder.schedule_picking_rect(
        ctx, picking_rect, 42, "My screenshot".to_owned(), false,
    );
}
fn receive_screenshots(ctx: &RenderContext) {
    while let Some(result) = PickingLayerProcessor::next_readback_result::<String>(ctx, 42) {
        re_log::info!("Received picking_data {}", result.user_data);
    }
}

Received data that isn’t retrieved for more than a frame will be automatically discarded.

pub fn composite(&self, ctx: &RenderContext, pass: &mut RenderPass<'_>)

Composites the final result of a ViewBuilder to a given output RenderPass.

The bound surface(s) on the RenderPass are expected to be the same format as specified on Context creation. screen_position specifies where on the output pass the view is placed.