在 glsl es 2.0、Gamemaker Studio 2.0 中获取渐变方块的问题

Question

我用 4 个三角形制作了一个三角形列表，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;
    }

游戏制作人代码：创建活动：

    //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。以下着色器平滑地将渐变从视图中间的圆形渐变更改为视图边界的方形渐变。使用 GLSL mix 函数将片段颜色从 color1 插值到 color2。

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));
}

预览：

在 glsl es 2.0、Gamemaker Studio 2.0 中获取渐变方块的问题

Issue getting gradient square in glsl es 2.0, Gamemaker Studio 2.0

opengl-es

glsl

shader

opengl-es-2.0

game-maker-studio-2