WebGL: drawArrays: attribs not setup correctly - html

Question

Here's my vertex shader:
attribute vec3 aVertexPosition;
attribute vec4 aVertexColor;
attribute float type;
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
varying vec4 vColor;
void main(void) {
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
vColor = aVertexColor;
if(type > 0.0) {
} else {
}
}
What I want to do is pretty simple, just capture a float value named type and use it for logic operates.
The problem is, when I try to use it in Javascript, the error comes:
shaderProgram.textureCoordAttribute = gl.getAttribLocation(shaderProgram, "type");
gl.enableVertexAttribArray(shaderProgram.textureCoordAttribute);
WebGL: INVALID_OPERATION: drawArrays: attribs not setup correctly main.js:253
WebGL: INVALID_OPERATION: drawArrays: attribs not setup correctly main.js:267
WebGL: INVALID_OPERATION: drawElements: attribs not setup correctly
The output of getAttribLocation is meaningful, all of them are equal greater than 0.
================= UPDATE ===================
Here's my whole project code:
https://gist.github.com/royguo/5873503
Explanation:
index.html Shaders script are here.
main.js Start the WebGL application and draw scene.
shaders.js Load shaders and bind attributes.
buffers.js Init vertex and color buffers.
utils.js Common used utils.

Answer 1

Here is a link to a gist with the files I updated to get the type attribute working.
If you search for //ADDED CODE you should be able to view every change I had to make to get it working.
In addition to enabling the objectTypeAttribute you have to create an array buffer for each object you are drawing:
triangleObjectTypeBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, triangleObjectTypeBuffer);
objectTypes = [
1.0, 1.0, 0.0
];
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(objectTypes), gl.STATIC_DRAW);
triangleObjectTypeBuffer.itemSize = 1;
triangleObjectTypeBuffer.numItems = 3;
And bind that array buffer for each object before you draw the object:
gl.bindBuffer(gl.ARRAY_BUFFER, triangleObjectTypeBuffer);
gl.vertexAttribPointer(shaderProgram.objectTypeAttribute, triangleObjectTypeBuffer.itemSize, gl.FLOAT, false, 0, 0);
You probably already tried this and accidentally went wrong somewhere along the way.