Hello, I made a 2D outline shader which works fine if I use it on a sprite from atlas with many sprites, but when the atlas has a few or only 1 sprite, then the outline from my shader becomes smaller.
Does anyone might know the reason for this behavior?
Shader’s fragment program code
#version 140
in vec2 var_texcoord0;
uniform sampler2D texture_sampler;
uniform input_data
{
// xyz - color, w - width
vec4 u_outline_settings;
};
out vec4 color_out;
void main()
{
vec4 texture_color = texture(texture_sampler, var_texcoord0);
if (texture_color.a != 0)
{
// check on each side of the current pixel, where to put an outline
float alpha = texture_color.a;
alpha += ceil(texture(texture_sampler, var_texcoord0 + vec2(u_outline_settings.w, 0.0)).a);
alpha += ceil(texture(texture_sampler, var_texcoord0 + vec2(-u_outline_settings.w, 0.0)).a);
alpha += ceil(texture(texture_sampler, var_texcoord0 + vec2(0.0, u_outline_settings.w)).a);
alpha += ceil(texture(texture_sampler, var_texcoord0 + vec2(0.0, -u_outline_settings.w)).a);
if (alpha != texture_color.a + 4.0)
{
float outline_usage = ceil(u_outline_settings.w);
// optional: " this gives better results, when filtering images or composing them "
vec4 outlined_texture_color = texture_color * texture_color.a;
// apply outline only where alpha is 0
vec4 colored_edge = vec4(u_outline_settings.xyz, 1.0);
outlined_texture_color += colored_edge;
texture_color = mix(texture_color, outlined_texture_color, outline_usage);
}
color_out = texture_color;
}
}
Result for the sprite when there is a 36 sprites (atlas size is 512x256)
Result for the sprite when there is only 7 sprite (atlas size is 256x256)
Result for the sprite when there is only 1 sprite (atlas size is 32x64)
