Add support for multiple bitmaps

[liyihongcug]

Thanks a lot for this software at first. Now I meet with one problem.I want to add different texture mapping bitmap in one cube. I search all codes many times. I choose Object3DBuilder .java.
Now it only support one bitmap. Can you help us realize add different texture mapping bitmap in one cube. (
bitmap[] bm.
bmp[0] = BitmapFactory.decodeResource(context.getResources(), R.drawable.aa);
bmp[1] = BitmapFactory.decodeResource(context.getResources(), R.drawable.bb);
bmp[2] = BitmapFactory.decodeResource(context.getResources(), R.drawable.cc);
bmp[3] = BitmapFactory.decodeResource(context.getResources(), R.drawable.dd);
bmp[4] = BitmapFactory.decodeResource(context.getResources(), R.drawable.ee);
bmp[5] = BitmapFactory.decodeResource(context.getResources(), R.drawable.ff)
not byte[] textureData and I want to change it to bimtap[]
)

file : Object3DBuilder.java
org.andresoviedo.app.model3D.model;public final class Object3DBuilder
public static Object3DData buildCubeV3(byte[] textureData) {
return new Object3DData(
createNativeByteBuffer(cubePositionData.length * 4).asFloatBuffer().put(cubePositionData),
createNativeByteBuffer(cubeTextureCoordinateData.length * 4).asFloatBuffer()
.put(cubeTextureCoordinateData).asReadOnlyBuffer(),
textureData).setDrawMode(GLES20.GL_TRIANGLES).setId("cubeV3").centerAndScale(1.0f);
}

[liyihongcug]

Another prolem:
I need only mapping one face texture mapping of 8 faces.
I try it and this software api can't support it. Please think it over.
I only handle with one texture mapping of many faces.

[andresoviedo]

Hey body. Support for multiple textures is not implemented.
I am wondering if it's possible to map all the cube faces with just 1 bitmap.
Gonna change the title to add the feature in the future ;)

[andresoviedo]

Ir order to support multiple textures there is 2 options:

1. Break the mesh into multiple objects, so you can map the texture independently to every object.

2. Map multiple textures into the FragmentShader, That is:

a. Load multiple textures into opengl. Change this method so you can load multiple textures (as many as you like) instead of only 1:
https://github.com/andresoviedo/android-3D-model-viewer/blob/master/app/src/main/java/org/andresoviedo/app/model3D/util/GLUtil.java#L104

final int[] textureId = new int[NUMBER_OF_TEXTURES_YOU_WANT];
GLES20.glGenTextures(1, textureId, 0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId[0]);
GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap0, 0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId[1]);
GLUtils.texImage2D(GLES20.GL_TEXTURE_2D, 0, bitmap1, 0);

...

b. In the vertex shader declare an attribute of type int to store the index of the texture unit to use and pass it to the fragment shader:

attribute int a_TexCoordinateUnit;
varying int v_TexCoordinateUnit;
void main(){
  v_TexCoordinateUnit = a_TexCoordinateUnit;
}

c. In the fragment shader, declare an array of sample2D (you may have at most 8 textures active)

uniform sampler2D u_Texture[8];
varying int v_TexCoordinateUnit;
void main(){
  gl_FragColor = v_Color * texture2D(u_Texture[v_TexCoordinateUnit], v_TexCoordinate);
}

d. Load the different texture units into OpenGL as many times as texture units you want to load (maximum 8):

GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId[0]);
GLES20.glUniform1i(mTextureUniformHandle, 0);

GLES20.glActiveTexture(GLES20.GL_TEXTURE1);
GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, textureId[1]);
GLES20.glUniform1i(mTextureUniformHandle, 1);

...
e. In the obj loader map every vertex with the corresponding texture into an IntBuffer (texture_unit_map)
f. Bind the texture_unit_map array into the vertex shader:

int mTextureCoordinateUnitHandle = GLES20.glGetAttribLocation(mProgram, "a_TexCoordinateUnit");
GLES20.glEnableVertexAttribArray(mTextureCoordinateUnitHandle );
obj.getTextureUnitMap().position(0);
GLES20.glVertexAttribPointer(mTextureCoordinateHandle, 1, GLES20.GL_INT, false, 0, obj.getTextureUnitMap());

[andresoviedo]

Dear @liyihongcug
Latest version of the app should solve most of the texture issues
so I am closing this for now
kind regards