如何直接配置PIXI.Graphics以低分辨率/更少顶点绘制图形提升性能？

Great question! I’ve dealt with this exact performance optimization in PIXI.js before, so I can share several practical, direct methods to cut down on vertex count or render at a lower resolution—no need for the "draw small then scale" workaround if you don’t want it.

1. Manually Control Vertex Precision for Curves/Shapes #

PIXI.Graphics often uses more vertices than necessary for curved shapes by default. You can explicitly reduce vertex count by adjusting parameters in drawing methods:

• Arcs/Circles: When using arc() or drawCircle(), the last optional parameter lets you set the number of segments. Instead of letting PIXI calculate it based on radius, pick a lower number (e.g., 8 instead of 20 for a circle that still looks smooth enough at scale):

  graphics.arc(x, y, radius, startAngle, endAngle, false, 8); // 8 segments instead of default
  

• Curves: For bezierCurveTo() or quadraticCurveTo(), you can approximate the curve with fewer points, or use drawPolygon() to manually define a simplified version of the curve.
• Polygons: If you’re drawing complex polygons, use a path simplification algorithm (like the Ramer-Douglas-Peucker algorithm) to remove redundant vertices before passing them to drawPolygon().

2. Offscreen Rendering with RenderTextures #

This is a more structured alternative to your current method, but it lets you render graphics at a lower resolution natively:

1. Create a RenderTexture at your target reduced resolution (e.g., half the screen size).
2. Draw your PIXI.Graphics to this texture instead of the main stage.
3. Display the texture in a sprite scaled up to full size.

Example code:

// Create a low-resolution render texture
const lowResTexture = PIXI.RenderTexture.create({
  width: window.innerWidth / 2,
  height: window.innerHeight / 2
});

// Draw your graphics
const myGraphics = new PIXI.Graphics();
myGraphics.beginFill(0xff3300);
myGraphics.drawRoundedRect(50, 50, 150, 100, 10);
myGraphics.endFill();

// Render graphics to the low-res texture
app.renderer.render(myGraphics, { renderTexture: lowResTexture });

// Display scaled up
const scaledSprite = new PIXI.Sprite(lowResTexture);
scaledSprite.scale.set(2);
app.stage.addChild(scaledSprite);

// Clean up if you don't need the original Graphics anymore
myGraphics.destroy();

3. Convert Graphics to a Texture (Static Shapes) #

If your graphics don’t need to update dynamically, converting them to a texture once and using a sprite is one of the most efficient methods. You can even set a lower resolution when generating the texture:

const staticGraphics = new PIXI.Graphics();
staticGraphics.beginFill(0x0066ff);
staticGraphics.drawEllipse(100, 100, 80, 50);
staticGraphics.endFill();

// Generate texture at 50% resolution
const graphicsTexture = staticGraphics.generateTexture({ resolution: 0.5 });

// Use sprite to display (scale up to match original size)
const textureSprite = new PIXI.Sprite(graphicsTexture);
textureSprite.scale.set(2);
app.stage.addChild(textureSprite);

// Destroy the original Graphics to free resources
staticGraphics.destroy();

4. Custom Mesh for Full Vertex Control #

For ultimate control, skip PIXI.Graphics entirely and use PIXI.Mesh with custom vertex data. You can define exactly which vertices to include, eliminating any overhead from PIXI’s automatic vertex generation. This is ideal for highly optimized, static shapes:

// Define your own vertices (e.g., a simplified triangle)
const vertices = new Float32Array([
  0, 0,     // Top-left
  200, 0,   // Top-right
  100, 150  // Bottom-center
]);

// Create a Mesh with a basic shader
const customMesh = new PIXI.Mesh(
  PIXI.Geometry.fromVertices(vertices),
  new PIXI.MeshBasicMaterial({ color: 0xffff00 })
);

customMesh.position.set(50, 50);
app.stage.addChild(customMesh);

Key Notes to Keep in Mind #

• Tradeoff: Lowering vertex count or resolution will reduce visual quality—test to find the balance between performance and appearance that works for your project.
• Dynamic vs Static: For shapes that update often, offscreen rendering with RenderTexture is better (just re-render the texture when changes happen). For static shapes, converting to a texture is the most efficient.
• PIXI Version: Some of these methods (like resolution parameters in generateTexture) are available in PIXI.js v5+.

内容的提问来源于stack exchange，提问作者jbjanot