base.geom

#version 450
/* Copyright (c) 2019-2024, Sascha Willems
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 the "License";
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

layout(points) in;
layout(triangle_strip, max_vertices = 24) out;

layout (location = 0) in vec3 gColor;
layout (location = 1) in mat4 modelViewProjection;
layout (location = 0) out vec3 fColor;

float voxSize = 0.5;

void AddQuad(vec4 center, vec4 dy, vec4 dx) {
    fColor = gColor;
    gl_Position = center + (dx - dy);
    EmitVertex();
    fColor = gColor;
    gl_Position = center + (-dx - dy);
    EmitVertex();
    fColor = gColor;
    gl_Position = center + (dx + dy);
    EmitVertex();
    fColor = gColor;
    gl_Position = center + (-dx + dy);
    EmitVertex();
    EndPrimitive();
}

/*
bool IsCulled(vec4 normal) {
    return normal.z > 0;
}
*/

void main() {
    vec4 center = gl_in[0].gl_Position;
    
    vec4 dx = modelViewProjection[0] / 2.0f * voxSize;
    vec4 dy = modelViewProjection[1] / 2.0f * voxSize;
    vec4 dz = modelViewProjection[2] / 2.0f * voxSize;
        AddQuad(center + dx, dy, dz);
        AddQuad(center - dx, dz, dy);
        AddQuad(center + dy, dz, dx);
        AddQuad(center - dy, dx, dz);
        AddQuad(center + dz, dx, dy);
        AddQuad(center - dz, dy, dx);
}