Avoid rendering outside WebGL layer and source extent

src/ol/layer/WebGLTile.js

@@ -96,12 +96,22 @@ function parseStyle(style, bandCount) {
   const vertexShader = `
     attribute vec2 ${Attributes.TEXTURE_COORD};
     uniform mat4 ${Uniforms.TILE_TRANSFORM};
+    uniform float ${Uniforms.TEXTURE_PIXEL_WIDTH};
+    uniform float ${Uniforms.TEXTURE_PIXEL_HEIGHT};
+    uniform float ${Uniforms.TEXTURE_RESOLUTION};
+    uniform float ${Uniforms.TEXTURE_ORIGIN_X};
+    uniform float ${Uniforms.TEXTURE_ORIGIN_Y};
     uniform float ${Uniforms.DEPTH};
 
     varying vec2 v_textureCoord;
+    varying vec2 v_mapCoord;
 
     void main() {
       v_textureCoord = ${Attributes.TEXTURE_COORD};
+      v_mapCoord = vec2(
+        ${Uniforms.TEXTURE_ORIGIN_X} + ${Uniforms.TEXTURE_RESOLUTION} * ${Uniforms.TEXTURE_PIXEL_WIDTH} * v_textureCoord[0],
+        ${Uniforms.TEXTURE_ORIGIN_Y} - ${Uniforms.TEXTURE_RESOLUTION} * ${Uniforms.TEXTURE_PIXEL_HEIGHT} * v_textureCoord[1]
+      );
       gl_Position = ${Uniforms.TILE_TRANSFORM} * vec4(${Attributes.TEXTURE_COORD}, ${Uniforms.DEPTH}, 1.0);
     }
   `;
@@ -237,6 +247,8 @@ function parseStyle(style, bandCount) {
     #endif
 
     varying vec2 v_textureCoord;
+    varying vec2 v_mapCoord;
+    uniform vec4 ${Uniforms.RENDER_EXTENT};
     uniform float ${Uniforms.TRANSITION_ALPHA};
     uniform float ${Uniforms.TEXTURE_PIXEL_WIDTH};
     uniform float ${Uniforms.TEXTURE_PIXEL_HEIGHT};
@@ -248,6 +260,15 @@ function parseStyle(style, bandCount) {
     ${functionDefintions.join('\n')}
 
     void main() {
+      if (
+        v_mapCoord[0] < ${Uniforms.RENDER_EXTENT}[0] ||
+        v_mapCoord[1] < ${Uniforms.RENDER_EXTENT}[1] ||
+        v_mapCoord[0] > ${Uniforms.RENDER_EXTENT}[2] ||
+        v_mapCoord[1] > ${Uniforms.RENDER_EXTENT}[3]
+      ) {
+        discard;
+      }
+
       vec4 color = texture2D(${
         Uniforms.TILE_TEXTURE_ARRAY
       }[0],  v_textureCoord);

src/ol/renderer/webgl/TileLayer.js

@@ -35,6 +35,10 @@ export const Uniforms = {
   DEPTH: 'u_depth',
   TEXTURE_PIXEL_WIDTH: 'u_texturePixelWidth',
   TEXTURE_PIXEL_HEIGHT: 'u_texturePixelHeight',
+  TEXTURE_RESOLUTION: 'u_textureResolution', // map units per texture pixel
+  TEXTURE_ORIGIN_X: 'u_textureOriginX', // map x coordinate of left edge of texture
+  TEXTURE_ORIGIN_Y: 'u_textureOriginY', // map y coordinate of top edge of texture
+  RENDER_EXTENT: 'u_renderExtent', // intersection of layer, source, and view extent
   RESOLUTION: 'u_resolution',
   ZOOM: 'u_zoom',
 };
@@ -150,7 +154,7 @@ class WebGLTileLayerRenderer extends WebGLLayerRenderer {
     this.renderComplete = false;
 
     /**
-     * This transform converts tile i, j coordinates to screen coordinates.
+     * This transform converts texture coordinates to screen coordinates.
      * @type {import("../../transform.js").Transform}
      * @private
      */
@@ -581,6 +585,19 @@ class WebGLTileLayerRenderer extends WebGLLayerRenderer {
           Uniforms.TEXTURE_PIXEL_HEIGHT,
           tileSize[1]
         );
+        this.helper.setUniformFloatValue(
+          Uniforms.TEXTURE_RESOLUTION,
+          tileResolution
+        );
+        this.helper.setUniformFloatValue(
+          Uniforms.TEXTURE_ORIGIN_X,
+          tileOrigin[0] + tileCenterI * tileSize[0] * tileResolution
+        );
+        this.helper.setUniformFloatValue(
+          Uniforms.TEXTURE_ORIGIN_Y,
+          tileOrigin[1] - tileCenterJ * tileSize[1] * tileResolution
+        );
+        this.helper.setUniformFloatVec4(Uniforms.RENDER_EXTENT, extent);
         this.helper.setUniformFloatValue(
           Uniforms.RESOLUTION,
           viewState.resolution

src/ol/webgl/Helper.js

@@ -962,6 +962,15 @@ class WebGLHelper extends Disposable {
     this.getGL().uniform1f(this.getUniformLocation(uniform), value);
   }
 
+  /**
+   * Give a value for a vec4 uniform
+   * @param {string} uniform Uniform name
+   * @param {Array<number>} value Array of length 4.
+   */
+  setUniformFloatVec4(uniform, value) {
+    this.getGL().uniform4fv(this.getUniformLocation(uniform), value);
+  }
+
   /**
    * Give a value for a standard matrix4 uniform
    * @param {string} uniform Uniform name