OpenGL缺少三角形的漫反射着色器

Question

I'm using C++ and when I implemented a diffuse shader, it causes every other triangle to disappear.

I can post my render code if need be, but I believe the issue is with my normal matrix (which I wrote it to be the transpose inverse of the model view matrix). Here is the shader code which is sort of similar to that of a tutorial on lighthouse tutorials. VERTEX SHADER

#version 330

layout(location=0) in vec3 position;
layout(location=1) in vec3 normal;

uniform mat4 transform_matrix;
uniform mat4 view_model_matrix;
uniform mat4 normal_matrix;
uniform vec3 light_pos;

out vec3 light_intensity;

void main()
{
    vec3 tnorm = normalize(normal_matrix * vec4(normal, 1.0)).xyz;
    vec4 eye_coords = transform_matrix * vec4(position, 1.0);
    vec3 s = normalize(vec3(light_pos - eye_coords.xyz)).xyz;

    vec3 light_set_intensity = vec3(1.0, 1.0, 1.0);
    vec3 diffuse_color = vec3(0.5, 0.5, 0.5);

    light_intensity = light_set_intensity * diffuse_color * max(dot(s, tnorm), 0.0);
    gl_Position = transform_matrix * vec4(position, 1.0);
}

My fragment shader just outputs the "light_intensity" in the form of a color. My model is straight from Blender and I have tried different exporting options like keeping vertex order, but nothing has worked.

Answer 1

This is not related to you shader.

It appears to be depth test related. Here, the order of triangles in the depth relative to you viewport is messed up, because you do not make sure that only the nearest pixel to your camera gets drawn.

Enable depth testing and make sure you have az buffer bound to your render target. Read more about this here: http://www.opengl.org/wiki/Depth_Test

Only the triangles highlighted in red should be visible to the viewer. Due to the lack of a valid depth test, there is no chance to guarantee, what triangle is painted top most. Thus blue triangles of the faces that should not be visible will cover parts of previously drawn red triangles.

The depth test would omit this, by comparing the depth in the z buffer with the depth of the pixel to be drawn at the current moment. Only the color information of a pixel that is closer to the viewer, ie has a smaller z value than the z value in the buffer, shall be written to the framebuffer in order to achieve a correct result.

(Backface culling, would be nice too and, if the model is correctly exported, also allow to show it correctly. But it would only hide the main problem, not solve it.)