opengl-es - 在 glsl es 2.0、Gamemaker Studio 2.0 中获取渐变正方形的问题

Question

我制作了一个包含 4 个三角形的三角形列表，中间点的颜色不同。然后旨在组合三角形以获得漂亮的渐变。但是三角形的边缘会产生不需要的线条，我不希望这些线条一直平滑。我怎样才能得到想要的结果？

图片：

着色器代码：

    // Simple passthrough vertex shader
    //
    attribute vec3 in_Position;                  // (x,y,z)
    attribute vec4 in_Colour;                    // (r,g,b,a)
    attribute vec2 in_TextureCoord;              // (u,v)

    varying vec2 v_texcoord;
    varying vec4 v_colour;

    void main()
    {
        vec4 object_space_pos = vec4( in_Position.x, in_Position.y,         in_Position.z, 1.0);
        gl_Position = gm_Matrices[MATRIX_WORLD_VIEW_PROJECTION] * object_space_pos;

        v_colour = in_Colour;
        v_texcoord = in_TextureCoord;
    }

    //
    // Simple passthrough fragment shader
    //
    varying vec2 v_texcoord;
    varying vec4 v_colour;

    void main()
    {
        gl_FragColor = v_colour;
    }

游戏制作者代码：创建事件：

    //Build vertices list


    vertex_format_begin();
    vertex_format_add_position();
    vertex_format_add_colour();
    vertex_format_add_textcoord();
    v_format = vertex_format_end();
    v_buff = vertex_create_buffer();
    vertex_begin(v_buff, v_format);

    //triangle 0
    vertex_position(v_buff, 200, 100);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 0.0, 0.0);

    vertex_position(v_buff, 600, 100);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 1.0, 0.0);

    vertex_position(v_buff,  400, 300);
    vertex_colour(v_buff, c_red, 1);
    vertex_texcoord(v_buff, 0.5, 0.5);

    //triangle 1
    vertex_position(v_buff, 200, 100);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 0.0, 0.0);

    vertex_position(v_buff, 200, 500);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 0.0, 1.0);

    vertex_position(v_buff,  400, 300);
    vertex_colour(v_buff, c_red, 1);
    vertex_texcoord(v_buff, 0.5, 0.5);

    //triangle 2
    vertex_position(v_buff, 600, 100);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 1.0, 0.0);

    vertex_position(v_buff, 600, 500);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 1.0, 1.0);

    vertex_position(v_buff,  400, 300);
    vertex_colour(v_buff, c_red, 1);
    vertex_texcoord(v_buff, 0.5, 0.5);

    //triangle 3
    vertex_position(v_buff, 200, 500);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 0.0, 1.0);

    vertex_position(v_buff, 600, 500);
    vertex_colour(v_buff, c_black, 1);
    vertex_texcoord(v_buff, 1.0, 1.0);

    vertex_position(v_buff,  400, 300);
    vertex_colour(v_buff, c_red, 1);
    vertex_texcoord(v_buff, 0.5, 0.5);

    vertex_end(v_buff);
    tex = sprite_get_texture(sprite_index, 0);

抽奖活动：

    shader_set(shd_prim);
    shader_set_uniform_f(uni_radius, var_radius);
    vertex_submit(v_buff, pr_trianglelist, tex);
    shader_reset();

Answer 1

您可以看到的效果是视错觉。您可以通过对颜色进行分级来使其可见。为此使用以下片段着色器：

varying vec2 v_texcoord;
varying vec4 v_colour;

void main()
{
    float steps   = 4.0;
    //float steps   = 8.0;
    //float steps   = 16.0;
    //float steps   = 32.0;

    vec3 gradColor = floor(v_colour.rgb * steps) / steps;
    gl_FragColor   = vec4(gradColor, 1.0);
}

4种颜色：

8种颜色：

16种颜色：

32 种颜色：

为了获得更好的结果，您必须在片段着色器中计算颜色。以下着色器平滑地更改渐变，从视图中间的圆形渐变到视图边界的方形渐变。使用 GLSL函数将片段颜色插值color1到。color2mix

varying vec2 v_texcoord;
varying vec4 v_colour;

void main()
{
    vec4 color1 = vec4(1.0, 0.0, 0.0, 1.0);
    vec4 color2 = vec4(0.0, 0.0, 0.0, 1.0);

    vec2 distV     = v_texcoord * 2.0 - 1.0;
    float maxDist  = max(abs(distV.x), abs(distV.y));
    float circular = length(distV);
    float square   = maxDist;

    gl_FragColor = mix(color1, color2, mix(circular,square,maxDist));
}

预习：