ColladaExporter: Convert vertex, material colors to sRGB before export (#23400)

* ColladaExporter: Convert vertex, material colors to sRGB before export

* convert specular color

examples/jsm/exporters/ColladaExporter.js

@@ -144,10 +144,31 @@ class ColladaExporter {
 
 		// gets the attribute array. Generate a new array if the attribute is interleaved
 		const getFuncs = [ 'getX', 'getY', 'getZ', 'getW' ];
+		const tempColor = new Color();
 
-		function attrBufferToArray( attr ) {
+		function attrBufferToArray( attr, isColor = false ) {
 
-			if ( attr.isInterleavedBufferAttribute ) {
+			console.log( attr, attr.count, isColor )
+			if ( isColor ) {
+
+				// convert the colors to srgb before export
+				// colors are always written as floats
+				const arr = new Float32Array( attr.count * 3 );
+				for ( let i = 0, l = attr.count; i < l; i ++ ) {
+
+					tempColor
+						.fromBufferAttribute( attr, i )
+						.convertLinearToSRGB();
+
+					arr[ 3 * i + 0 ] = tempColor.r;
+					arr[ 3 * i + 1 ] = tempColor.g;
+					arr[ 3 * i + 2 ] = tempColor.b;
+
+				}
+
+				return arr;
+
+			} else if ( attr.isInterleavedBufferAttribute ) {
 
 				// use the typed array constructor to save on memory
 				const arr = new attr.array.constructor( attr.count * attr.itemSize );
@@ -183,9 +204,9 @@ class ColladaExporter {
 		}
 
 		// Returns the string for a geometry's attribute
-		function getAttribute( attr, name, params, type ) {
+		function getAttribute( attr, name, params, type, isColor = false ) {
 
-			const array = attrBufferToArray( attr );
+			const array = attrBufferToArray( attr, isColor );
 			const res =
 					`<source id="${ name }">` +
 
@@ -296,8 +317,9 @@ class ColladaExporter {
 				// serialize colors
 				if ( 'color' in bufferGeometry.attributes ) {
 
+					// colors are always written as floats
 					const colName = `${ meshid }-color`;
-					gnode += getAttribute( bufferGeometry.attributes.color, colName, [ 'X', 'Y', 'Z' ], 'uint8' );
+					gnode += getAttribute( bufferGeometry.attributes.color, colName, [ 'R', 'G', 'B' ], 'float', true );
 					triangleInputs += `<input semantic="COLOR" source="#${ colName }" offset="0" />`;
 
 				}
@@ -419,6 +441,10 @@ class ColladaExporter {
 				const shininess = m.shininess || 0;
 				const reflectivity = m.reflectivity || 0;
 
+				emissive.convertLinearToSRGB();
+				specular.convertLinearToSRGB();
+				diffuse.convertLinearToSRGB();
+
 				// Do not export and alpha map for the reasons mentioned in issue (#13792)
 				// in three.js alpha maps are black and white, but collada expects the alpha
 				// channel to specify the transparency