.mtl files support for .obj files to render color in 3D custom geometry

src/webgl/loading.js

@@ -103,6 +103,8 @@ import './p5.Geometry';
  * @param  {String} [fileType]
  * @return {p5.Geometry} the <a href="#/p5.Geometry">p5.Geometry</a> object
  */
+
+let materials = {}; //currently local
 p5.prototype.loadModel = function(path) {
   p5._validateParameters('loadModel', arguments);
   let normalize;
@@ -150,16 +152,38 @@ p5.prototype.loadModel = function(path) {
   } else if (fileType.match(/\.obj$/i)) {
     this.loadStrings(
       path,
-      strings => {
-        parseObj(model, strings);
-
-        if (normalize) {
-          model.normalize();
+      async lines => {
+        const mtlLine = lines.find(line => line.startsWith('mtllib '));
+
+        // console.log(mtlPath);
+        try{
+          let parsedMaterials=null;
+          if(mtlLine){
+            const mtlPath = path.replace(/\.obj$/, '.mtl');
+            parsedMaterials=await parseMtl(mtlPath);  // Pass parsed materials to OBJ parsing
+          }
+          if (parsedMaterials){
+            await parseObj(model,lines, parsedMaterials);
+          }else {
+            await parseObj(model,lines); // No MTL file, parse OBJ directly
+          }
+        } catch (error) {
+          if (failureCallback) {
+            failureCallback(error);
+          } else {
+            p5._friendlyError('Error during parsing: ' + error.message);
+          }
         }
+        finally{
 
-        self._decrementPreload();
-        if (typeof successCallback === 'function') {
-          successCallback(model);
+          if (normalize) {
+            model.normalize();
+          }
+
+          self._decrementPreload();
+          if (typeof successCallback === 'function') {
+            successCallback(model);
+          }
         }
       },
       failureCallback
@@ -178,6 +202,54 @@ p5.prototype.loadModel = function(path) {
   return model;
 };
 
+function parseMtl(mtlPath){ //accepts mtlPath to load file
+  return new Promise((resolve,reject)=>{
+    // console.log('parser is called');
+    let currentMaterial = null;
+    p5.prototype.loadStrings(
+      mtlPath,
+      lines => {
+        for (let line = 0; line < lines.length; ++line){
+          const tokens = lines[line].trim().split(/\s+/);
+          if(tokens[0] === 'newmtl') {
+            const materialName = tokens[1];
+            currentMaterial = materialName;
+            materials[currentMaterial] = {};
+          }else if (tokens[0] === 'Kd'){
+            //Diffuse color
+            materials[currentMaterial].diffuseColor = [
+              parseFloat(tokens[1]),
+              parseFloat(tokens[2]),
+              parseFloat(tokens[3])
+            ];
+          } else if (tokens[0] === 'Ka'){
+            //Ambient Color
+            materials[currentMaterial].ambientColor = [
+              parseFloat(tokens[1]),
+              parseFloat(tokens[2]),
+              parseFloat(tokens[3])
+            ];
+          }else if (tokens[0] === 'Ks'){
+            //Specular color
+            materials[currentMaterial].specularColor = [
+              parseFloat(tokens[1]),
+              parseFloat(tokens[2]),
+              parseFloat(tokens[3])
+            ];
+
+          }else if (tokens[0] === 'map_Kd') {
+            //Texture path
+            materials[currentMaterial].texturePath = tokens[1];
+          }
+        }
+        resolve(materials);
+      },
+      reject
+    );
+  });
+
+}
+
 /**
  * Parse OBJ lines into model. For reference, this is what a simple model of a
  * square might look like:
@@ -189,7 +261,7 @@ p5.prototype.loadModel = function(path) {
  *
  * f 4 3 2 1
  */
-function parseObj(model, lines) {
+function parseObj(model, lines, materials= {}) {
   // OBJ allows a face to specify an index for a vertex (in the above example),
   // but it also allows you to specify a custom combination of vertex, UV
   // coordinate, and vertex normal. So, "3/4/3" would mean, "use vertex 3 with
@@ -205,6 +277,8 @@ function parseObj(model, lines) {
     vn: []
   };
   const indexedVerts = {};
+  let currentMaterial = null;
+
 
   for (let line = 0; line < lines.length; ++line) {
     // Each line is a separate object (vertex, face, vertex normal, etc)
@@ -213,7 +287,20 @@ function parseObj(model, lines) {
     const tokens = lines[line].trim().split(/\b\s+/);
 
     if (tokens.length > 0) {
-      if (tokens[0] === 'v' || tokens[0] === 'vn') {
+      if (tokens[0] === 'usemtl') {
+        // Switch to a new material
+        currentMaterial = tokens[1];
+        if (currentMaterial && materials[currentMaterial]) {
+          const diffuseColor = materials[currentMaterial].diffuseColor;
+          model.vertexColors.push([
+            diffuseColor[0],
+            diffuseColor[1],
+            diffuseColor[2]
+          ]);
+        } else {
+          model.vertexColors.push([1, 1, 1]);
+        }
+      }else if (tokens[0] === 'v' || tokens[0] === 'vn') {
         // Check if this line describes a vertex or vertex normal.
         // It will have three numeric parameters.
         const vertex = new p5.Vector(
@@ -285,7 +372,6 @@ function parseObj(model, lines) {
   if (model.vertexNormals.length === 0) {
     model.computeNormals();
   }
-
   return model;
 }
 

test/unit/assets/octa-color.mtl

@@ -0,0 +1,72 @@
+newmtl m000001
+Ns 100
+Kd 0 0 0.5
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m003627
+Ns 100
+Kd 0 0 0.942654
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m010778
+Ns 100
+Kd 0 0.815632 1
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m012003
+Ns 100
+Kd 0 0.965177 1
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m019240
+Ns 100
+Kd 0.848654 1 0.151346
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m021392
+Ns 100
+Kd 1 0.888635 0
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m022299
+Ns 100
+Kd 1 0.77791 0
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+
+newmtl m032767
+Ns 100
+Kd 0.5 0 0
+Ks 1 1 1
+Ka 0 0 0
+Ni 1
+d 1
+illum 2
+

test/unit/assets/octa-color.obj

@@ -0,0 +1,23 @@
+mtllib octa-color.mtl
+v 1 0 0
+v 0 1 0
+v 0 0 1
+v -1 0 0
+v 0 -1 0
+v 0 0 -1
+usemtl m000001
+f 1 5 6
+usemtl m003627
+f 2 1 6
+usemtl m010778
+f 1 2 3
+usemtl m012003
+f 4 2 6
+usemtl m019240
+f 4 5 3
+usemtl m021392
+f 5 4 6
+usemtl m022299
+f 2 4 3
+usemtl m032767
+f 5 1 3