Single shader to draw objects in different modes?

Hi,

I’m trying to make 3 different stage, first drawing only then add lighting and finally texture.
So that I can switch among 3 modes, can this be achieved by one single shader? or it has to be separated?

Many thanks!

[Drawing + No Lighting]

I couldn’t figure this out yet

[Drawing + Lighting]

[Drawing + Lighting + Texture]

[Vertex Shader]

#version 450 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;

out VS_OUT {
    vec3 FragPos;
    vec3 Normal;
    vec2 TexCoords;
} vs_out;

uniform mat4 projection;
uniform mat4 view;
uniform mat4 model;

void main() {
    vs_out.FragPos = vec3(model * vec4(aPos, 1.0));   
    vs_out.TexCoords = aTexCoords;
        
    mat3 normalMatrix = transpose(inverse(mat3(model)));
    vs_out.Normal = normalize(normalMatrix * aNormal);
    
    gl_Position = projection * view * model * vec4(aPos, 1.0);
}

[Fragment Shader]

#version 450 core
layout (location = 0) out vec4 FragColor;
layout (location = 1) out vec4 BrightColor;

in VS_OUT {
    vec3 FragPos;
    vec3 Normal;
    vec2 TexCoords;
} fs_in;

struct Light {
    vec3 Position;
    vec3 Color;
};

uniform Light lights[4];
uniform sampler2D diffuseTexture;
uniform bool withLight;
uniform bool withTexture;
uniform vec3 viewPos;

out vec4 FragColor;

void main() {
    vec3 color;
    if (withTexture)
        color = texture(diffuseTexture, fs_in.TexCoords).rgb;

    else
        color = vec3(0.45, 0.45, 0.45);

    vec3 normal = normalize(fs_in.Normal);
    
    // Ambient
    vec3 ambient = 0.0 * color;
    
    // Lighting
    vec3 lighting = vec3(0.0);
    vec3 viewDir = normalize(viewPos - fs_in.FragPos);
    
    for (int i = 0; i < 4; i++) {
        // Diffuse
        vec3 lightDir = normalize(lights[i].Position - fs_in.FragPos);
        float diff = max(dot(lightDir, normal), 0.0);
        vec3 result = lights[i].Color * diff * color;
        
        // Attenuation (use quadratic as we have gamma correction)
        float distance = length(fs_in.FragPos - lights[i].Position);
        result *= 1.0 / (distance * distance);
        lighting += result;          
    }

    vec3 result = ambient + lighting;

    // Check whether result is higher than some threshold, if so, output as threshold color
    float brightness = dot(result, vec3(0.2126, 0.7152, 0.0722));
    
    if (brightness > 1.0)
        BrightColor = vec4(result, 1.0);
    
    else
        BrightColor = vec4(0.0, 0.0, 0.0, 1.0);
    
    FragColor = vec4(result, 1.0);
}

If you make the ambient lighting colour a uniform variable, you can just set ambient to (1,1,1) and the light colour to (0,0,0) to get “no lighting”.

Similarly, you can use a 1x1 white texture to get “no texture”.

1 Like

Thanks so much!!!
I was able to achieve the goal with your kind help :slight_smile: