diff --git a/addons/addon-webgl/src/customGlyphs/CustomGlyphDefinitions.ts b/addons/addon-webgl/src/customGlyphs/CustomGlyphDefinitions.ts
index 1a77d86f..601ff6a7 100644
--- a/addons/addon-webgl/src/customGlyphs/CustomGlyphDefinitions.ts
+++ b/addons/addon-webgl/src/customGlyphs/CustomGlyphDefinitions.ts
@@ -499,7 +499,22 @@ export const customGlyphDefinitions: { [index: string]: CustomGlyphCharacterDefi
 
   // Triangular shade characters (1FB9C-1FB9F)
 
-  // TODO: Implement
+  '\u{1FB9C}': { type: CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_CLIP_PATH, data: [[ // UPPER LEFT TRIANGULAR MEDIUM SHADE
+    [1, 0],
+    [0, 1]
+  ], 'M0,0 L1,0 L0,1 Z'] },
+  '\u{1FB9D}': { type: CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_CLIP_PATH, data: [[ // UPPER RIGHT TRIANGULAR MEDIUM SHADE
+    [1, 0],
+    [0, 1]
+  ], 'M0,0 L1,0 L1,1 Z'] },
+  '\u{1FB9E}': { type: CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_CLIP_PATH, data: [[ // LOWER RIGHT TRIANGULAR MEDIUM SHADE
+    [1, 0],
+    [0, 1]
+  ], 'M1,0 L1,1 L0,1 Z'] },
+  '\u{1FB9F}': { type: CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_CLIP_PATH, data: [[ // LOWER LEFT TRIANGULAR MEDIUM SHADE
+    [1, 0],
+    [0, 1]
+  ], 'M0,0 L1,1 L0,1 Z'] },
 
   // Character cell diagonals (1FBA0-1FBAE)
   '\u{1FBA0}': { type: CustomGlyphDefinitionType.PATH_FUNCTION_WITH_WEIGHT, data: { [FontWeight.NORMAL]: 'M.5,0 L0,.5' } }, // BOX DRAWINGS LIGHT DIAGONAL UPPER CENTRE TO MIDDLE LEFT
diff --git a/addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.ts b/addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.ts
index 549230ad..495bc70e 100644
--- a/addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.ts
+++ b/addons/addon-webgl/src/customGlyphs/CustomGlyphRasterizer.ts
@@ -37,6 +37,9 @@ export function tryDrawCustomGlyph(
         drawBlockPatternWithRegion(ctx, unifiedCharDefinition.data.pattern, xOffset, yOffset, deviceCellWidth, deviceCellHeight);
         drawBlockVectorChar(ctx, unifiedCharDefinition.data.vectors, xOffset, yOffset, deviceCellWidth, deviceCellHeight);
         return true;
+      case CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_CLIP_PATH:
+        drawBlockPatternWithClipPath(ctx, unifiedCharDefinition.data, xOffset, yOffset, deviceCellWidth, deviceCellHeight);
+        return true;
       case CustomGlyphDefinitionType.PATH_FUNCTION:
       case CustomGlyphDefinitionType.PATH:
         drawPathDefinitionCharacter(ctx, unifiedCharDefinition.data, xOffset, yOffset, deviceCellWidth, deviceCellHeight);
@@ -286,6 +289,49 @@ function drawPathDefinitionCharacterWithWeight(
   }
 }
 
+/**
+ * Draws a pattern clipped to an arbitrary path (for triangular shades, etc.)
+ */
+function drawBlockPatternWithClipPath(
+  ctx: CanvasRenderingContext2D,
+  definition: [pattern: CustomGlyphPatternDefinition, clipPath: string],
+  xOffset: number,
+  yOffset: number,
+  deviceCellWidth: number,
+  deviceCellHeight: number
+): void {
+  const [pattern, clipPath] = definition;
+
+  ctx.save();
+
+  // Build clip path from SVG-like instructions
+  ctx.beginPath();
+  for (const instruction of clipPath.split(' ')) {
+    const type = instruction[0];
+    if (type === 'Z') {
+      ctx.closePath();
+      continue;
+    }
+    const args: string[] = instruction.substring(1).split(',');
+    if (!args[0] || !args[1]) {
+      continue;
+    }
+    const x = xOffset + parseFloat(args[0]) * deviceCellWidth;
+    const y = yOffset + parseFloat(args[1]) * deviceCellHeight;
+    if (type === 'M') {
+      ctx.moveTo(x, y);
+    } else if (type === 'L') {
+      ctx.lineTo(x, y);
+    }
+  }
+  ctx.clip();
+
+  // Draw the pattern
+  drawPatternChar(ctx, pattern, xOffset, yOffset, deviceCellWidth, deviceCellHeight);
+
+  ctx.restore();
+}
+
 function drawVectorShape(
   ctx: CanvasRenderingContext2D,
   charDefinition: ICustomGlyphVectorShape,
diff --git a/addons/addon-webgl/src/customGlyphs/Types.ts b/addons/addon-webgl/src/customGlyphs/Types.ts
index bfe5155a..4623ea46 100644
--- a/addons/addon-webgl/src/customGlyphs/Types.ts
+++ b/addons/addon-webgl/src/customGlyphs/Types.ts
@@ -35,6 +35,7 @@ export const enum CustomGlyphDefinitionType {
   BLOCK_PATTERN,
   BLOCK_PATTERN_WITH_REGION,
   BLOCK_PATTERN_WITH_REGION_AND_SOLID_OCTANT_BLOCK_VECTOR,
+  BLOCK_PATTERN_WITH_CLIP_PATH,
   PATH_FUNCTION,
   PATH_FUNCTION_WITH_WEIGHT,
   PATH,
@@ -50,6 +51,7 @@ export type CustomGlyphCharacterDefinition = (
   // TODO: Consolidate these, draws should be possible via regions/clipping instead of special
   // casing
   { type: CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_REGION_AND_SOLID_OCTANT_BLOCK_VECTOR, data: { pattern: [pattern: CustomGlyphPatternDefinition, region: CustomGlyphRegionDefinition], vectors: ICustomGlyphSolidOctantBlockVector[] } } |
+  { type: CustomGlyphDefinitionType.BLOCK_PATTERN_WITH_CLIP_PATH, data: [pattern: CustomGlyphPatternDefinition, clipPath: string] } |
   { type: CustomGlyphDefinitionType.PATH_FUNCTION, data: CustomGlyphPathDrawFunctionDefinition } |
   { type: CustomGlyphDefinitionType.PATH_FUNCTION_WITH_WEIGHT, data: { [fontWeight: number]: string | CustomGlyphPathDrawFunctionDefinition } } |
   { type: CustomGlyphDefinitionType.PATH, data: string } |