Question about load and render Wavefront OBJ with multi textures？

[Richard-coder]

I have a Wavefront OBJ model with two texttures, like following.

Model.mtl
Model.obj
Model0_0000.png
Model1_0000.png

I can load the model successfully, but while I try to render the model, I can only get the render view with one texture. If i usetexture_0, I can get scene view with Model0_0000.png correctly. If i usetexture_1, I can get scene view with Model1_0000.png correctly. I can't get scene view with Model0_0000.png and Model1_0000.png together correctly.

I'm sure the obj file has no problem, because it can be rendered correctly by MeshLab and Open3D.

Do you have any advice? Thank you!

const std::string default_model_shader = R"Shader(
/////////////////////////////////////////
@start vertex
#version 120

#expect SHOW_COLOR
#expect SHOW_NORMAL
#expect SHOW_TEXTURE
#expect SHOW_MATCAP
#expect SHOW_UV

    uniform mat4 T_cam_norm;
    uniform mat4 KT_cw;
    attribute vec3 vertex;

#if SHOW_COLOR
    attribute vec4 color;
    varying vec4 vColor;
    void main() {
        vColor = color;
#elif SHOW_NORMAL
    attribute vec3 normal;
    varying vec3 vNormal;
    void main() {
        vNormal = mat3(T_cam_norm) * normal;
#elif SHOW_TEXTURE
    attribute vec2 uv;
    varying vec2 vUV;
    void main() {
        vUV = uv;
#elif SHOW_MATCAP
    attribute vec3 normal;
    varying vec3 vNormalCam;
    void main() {
        vNormalCam = mat3(T_cam_norm) * normal;
#elif SHOW_UV
    attribute vec2 uv;
    varying vec2 vUV;
    void main() {
        vUV = uv;
#else
    varying vec3 vP;
    void main() {
        vP = vertex;
#endif
        gl_Position = KT_cw * vec4(vertex, 1.0);
    }

/////////////////////////////////////////
@start fragment
#version 120
#expect SHOW_COLOR
#expect SHOW_NORMAL
#expect SHOW_TEXTURE
#expect SHOW_MATCAP
#expect SHOW_UV

#if SHOW_COLOR
    varying vec4 vColor;
#elif SHOW_NORMAL
    varying vec3 vNormal;
#elif SHOW_TEXTURE
    varying vec2 vUV;
    uniform sampler2D texture_0;
#elif SHOW_MATCAP
    varying vec3 vNormalCam;
    uniform sampler2D matcap;
#elif SHOW_UV
    varying vec2 vUV;
#else
    varying vec3 vP;
#endif

void main() {
#if SHOW_COLOR
    gl_FragColor = vColor;
#elif SHOW_NORMAL
    gl_FragColor = vec4((vNormal + vec3(1.0,1.0,1.0)) / 2.0, 1.0);
#elif SHOW_TEXTURE
    gl_FragColor = texture2D(texture_0, vUV);
#elif SHOW_MATCAP
    vec2 uv = 0.5 * vNormalCam.xy + vec2(0.5, 0.5);
    gl_FragColor = texture2D(matcap, uv);
#elif SHOW_UV
    gl_FragColor = vec4(vUV,1.0-vUV.x,1.0);
#else
    gl_FragColor = vec4(vP / 100.0,1.0);
#endif
}
)Shader";

[stevenlovegrove]

You're right, unfortunately Pangolin does not support multi-texture loading for objects right now. It gets most of the needed info through to the shader, but the shader needs some extra logic to pick between them, as you have discovered.