在OpenGL中为地形生成平滑法线

Question

我正在实施一种使用Perlin噪声生成地形的系统。这是我生成顶点的方式：

int arrayIdx = 0;

    for(float x = offset.x - CHUNK_WIDTH / 2.0f; x < float(CHUNK_WIDTH) + offset.x - CHUNK_WIDTH / 2.0f; x += TRIANGLE_WIDTH) {
        for(float y = offset.y - CHUNK_WIDTH / 2.0f; y < float(CHUNK_WIDTH) + offset.y - CHUNK_WIDTH / 2.0f; y += TRIANGLE_WIDTH) {
            float height0 = noise->octaveNoise(x + 0.0f * TRIANGLE_WIDTH, y + 0.0f * TRIANGLE_WIDTH),
            height1 = noise->octaveNoise(x + 1.0f * TRIANGLE_WIDTH, y + 0.0f * TRIANGLE_WIDTH),
            height2 = noise->octaveNoise(x + 0.0f * TRIANGLE_WIDTH, y + 1.0f * TRIANGLE_WIDTH),
            height3 = noise->octaveNoise(x + 1.0f * TRIANGLE_WIDTH, y + 1.0f * TRIANGLE_WIDTH);

            mapVertices[arrayIdx + 0] = glm::vec3(x + 0.0f * TRIANGLE_WIDTH, height0, y + 0.0f * TRIANGLE_WIDTH);
            mapVertices[arrayIdx + 1] = glm::vec3(x + 1.0f * TRIANGLE_WIDTH, height1, y + 0.0f * TRIANGLE_WIDTH);
            mapVertices[arrayIdx + 2] = glm::vec3(x + 0.0f * TRIANGLE_WIDTH, height2, y + 1.0f * TRIANGLE_WIDTH);
            mapVertices[arrayIdx + 3] = glm::vec3(x + 1.0f * TRIANGLE_WIDTH, height3, y + 1.0f * TRIANGLE_WIDTH);
            mapVertices[arrayIdx + 4] = glm::vec3(x + 1.0f * TRIANGLE_WIDTH, height1, y + 0.0f * TRIANGLE_WIDTH);
            mapVertices[arrayIdx + 5] = glm::vec3(x + 0.0f * TRIANGLE_WIDTH, height2, y + 1.0f * TRIANGLE_WIDTH);

            mapUVs[arrayIdx + 0] = glm::vec2(x + 0.0f * TRIANGLE_WIDTH, y + 0.0f * TRIANGLE_WIDTH);
            mapUVs[arrayIdx + 1] = glm::vec2(x + 1.0f * TRIANGLE_WIDTH, y + 0.0f * TRIANGLE_WIDTH);
            mapUVs[arrayIdx + 2] = glm::vec2(x + 0.0f * TRIANGLE_WIDTH, y + 1.0f * TRIANGLE_WIDTH);
            mapUVs[arrayIdx + 3] = glm::vec2(x + 1.0f * TRIANGLE_WIDTH, y + 1.0f * TRIANGLE_WIDTH);
            mapUVs[arrayIdx + 4] = glm::vec2(x + 1.0f * TRIANGLE_WIDTH, y + 0.0f * TRIANGLE_WIDTH);
            mapUVs[arrayIdx + 5] = glm::vec2(x + 0.0f * TRIANGLE_WIDTH, y + 1.0f * TRIANGLE_WIDTH);



            glm::vec3 normal0 = -1.0f * glm::triangleNormal(mapVertices[arrayIdx + 0], mapVertices[arrayIdx + 1], mapVertices[arrayIdx + 2]),
            normal1 = +1.0f * glm::triangleNormal(mapVertices[arrayIdx + 3], mapVertices[arrayIdx + 4], mapVertices[arrayIdx + 5]);

            mapNormals[arrayIdx + 0] = normal0;
            mapNormals[arrayIdx + 1] = (normal0 + normal1) / 2.0f;
            mapNormals[arrayIdx + 2] = (normal0 + normal1) / 2.0f;
            mapNormals[arrayIdx + 3] = normal1;
            mapNormals[arrayIdx + 4] = (normal0 + normal1) / 2.0f;
            mapNormals[arrayIdx + 5] = (normal0 + normal1) / 2.0f;


            arrayIdx += 6;
        }
    }

不使用照明会产生非常平滑的结果，

唯一要做的就是为三角形生成法线，这将使地形看起来很平滑。仅使用glm::triangleNormal即可得出此结果，

如您所见，照明确实破坏了光滑表面的幻觉。

我尝试在这样的三角形的碰撞顶点上使用法线的平均值：

arrayIdx = 0;

    for(float x = offset.x - CHUNK_WIDTH / 2.0f; x < float(CHUNK_WIDTH) + offset.x - CHUNK_WIDTH / 2.0f; x += TRIANGLE_WIDTH) {
        for(float y = offset.y - CHUNK_WIDTH / 2.0f; y < float(CHUNK_WIDTH) + offset.y - CHUNK_WIDTH / 2.0f; y += TRIANGLE_WIDTH) {

            if((x == offset.x - CHUNK_WIDTH / 2.0f && y == offset.y - CHUNK_WIDTH / 2.0f) ||
               (x == float(CHUNK_WIDTH) + offset.x - CHUNK_WIDTH / 2.0f - TRIANGLE_WIDTH && y == offset.y - CHUNK_WIDTH / 2.0f) ||
               (x == offset.x - CHUNK_WIDTH / 2.0f && y ==  float(CHUNK_WIDTH) + offset.y - CHUNK_WIDTH / 2.0f - TRIANGLE_WIDTH) ||
               (x == float(CHUNK_WIDTH) + offset.x - CHUNK_WIDTH / 2.0f - TRIANGLE_WIDTH && y ==  float(CHUNK_WIDTH) + offset.y - CHUNK_WIDTH / 2.0f - TRIANGLE_WIDTH)) {
                //Special case
            }
            else if(x ==  float(CHUNK_WIDTH) + offset.x - CHUNK_WIDTH / 2.0f - TRIANGLE_WIDTH ||
                    y ==  float(CHUNK_WIDTH) + offset.y - CHUNK_WIDTH / 2.0f - TRIANGLE_WIDTH) {
                 //Special case
            }
            else {
                glm::vec3 averageNormals = (mapNormals[arrayIdx + 3 + 0] + //This triangle
                                            mapNormals[arrayIdx + 0 + int(CHUNK_WIDTH * (1.0f / TRIANGLE_WIDTH)) * 6 + 6] + //Triangle after and this one
                                            mapNormals[arrayIdx + 2 + 6] + //Triangle in the right
                                            mapNormals[arrayIdx + 5 + 6] + //Triangle in the right
                                            mapNormals[arrayIdx + 1 + int(CHUNK_WIDTH * (1.0f / TRIANGLE_WIDTH)) * 6] + //Triangle after this one
                                            mapNormals[arrayIdx + 4 + int(CHUNK_WIDTH * (1.0f / TRIANGLE_WIDTH)) * 6])  //Triangle after this one
                                            / 6.0f;

                mapNormals[arrayIdx + 3 + 0] = averageNormals;
                mapNormals[arrayIdx + 2 + 6] = mapNormals[arrayIdx + 3 + 0];
                mapNormals[arrayIdx + 5 + 6] = mapNormals[arrayIdx + 3 + 0];
                mapNormals[arrayIdx + 1 + int(CHUNK_WIDTH * (1.0f / TRIANGLE_WIDTH)) * 6] = mapNormals[arrayIdx + 3 + 0];
                mapNormals[arrayIdx + 4 + int(CHUNK_WIDTH * (1.0f / TRIANGLE_WIDTH)) * 6] = mapNormals[arrayIdx + 3 + 0];
                mapNormals[arrayIdx + 0 + int(CHUNK_WIDTH * (1.0f / TRIANGLE_WIDTH)) * 6 + 6] = mapNormals[arrayIdx + 3 + 0];
            }

            arrayIdx += 6;
        }
    }

产生了这个结果，