Crate gfx_draping

A library for rendering polygons onto 3d terrain.

This crate uses a screen-space algorithm; it uses your GPU's stencil buffer to detect pixels where the polygon lies on terrain unoccluded. In addition, this crate is meant for drawing multiple polygons at once. If you have a collection of polygons which may need to be drawn simultaneously, put them all in a PolygonBuffer. You can choose which of those polygons to render by combining their respective PolygonBufferIndices.

Typically, usage of this crate will look something like:

extern crate geo;
extern crate gfx_draping;

use gfx_draping::{DrapingRenderer, PolygonBuffer, PolygonBufferIndices};

// Let's say you're using `geo` (a Rust GIS crate) to construct polygons.
let polygons: Vec<geo::Polygon> = a_vec_of_polygons();

// Prepare assets for rendering.
let mut buffer = PolygonBuffer::new();
let mut indices = PolygonBufferIndices::new();
for polygon in polygons {
    indices.extend(buffer.add(polygon.into()));
}

let renderer = DrapingRenderer::new();
let renderable_buffer = buffer.as_renderable(&mut window.factory);
let renderable_indices = indices.as_renderable(&mut window.factory);

while your_event_loop() {
    // Render your 3d terrain
    render_terrain();

    // At this point, your depth stencil should be the result of drawing the terrain. Your
    // stencil buffer should be all zeroes.
    renderer.render(
        window.encoder,
        window.output_color,
        window.output_stencil,
        // See docs for `DrapingRenderer::render` for a caveat about what `mvp` should be.
        your_scaled_mvp(),
        // R - G - B - A
        [1.0, 0.0, 1.0, 0.5],
        &renderable_buffer,
        &renderable_indices,
    );

    // Now you can clear / clean-up as you do usually.
}

Structs

DrapingRenderer	Drives graphics operations.
Polygon	A polygon with a bounding box.
PolygonBuffer	A collection of polygons that could all be rendered in a single draw call.
PolygonBufferIndices	A set of indices into a PolygonBuffer.
RenderablePolygonBuffer	A set of vertex buffer handles ready for rendering.
RenderablePolygonIndices	A set of index buffer handles ready for rendering.