试图重现一个Unity的树叶Shader，但是效果不正确

Creator 3.x
#1
  • Creator 版本： 3.8.2
  • 目标平台：目前测试在Editor和PC网页，目标是微信小游戏（还没测试）
  • 重现方式：
    在Unity实现的一个树叶从效果，Shader算法具体如下：
    image
    具体效果是：
    Unity_2024-05-27_11-34-59
    模型网格的UV是：
    image
    技术相关视频：
    https://www.bilibili.com/video/BV1w34y1D7bp/

Cocos从Unlit修改过来，相关代码为：
vec4 vert () {
vec4 position;
CCVertInput(position);
mat4 matWorld;
mat4 matWorldInv;
CCGetWorldMatrixFull(matWorld, matWorldInv);
v_uv = a_texCoord * tilingOffset.xy + tilingOffset.zw;

#if SAMPLE_FROM_RT
  CC_HANDLE_RT_SAMPLE_FLIP(v_uv);
#endif

// 树叶
vec2 remapUV = mix(vec2(-1.0), vec2(1.0), v_uv.xy);
vec4 remapUV_WS = vec4(remapUV, 0.0, 0.0);
vec4 _remapUV = matWorldInv * cc_matViewInv * remapUV_WS * -1.0;
position.xyz += _remapUV.xyz;

//…

但是具体实现之后和Unity有偏差，物体自身旋转的时候广告版就失效了：
CocosCreator_2024-05-27_11-48-03

#3

确认一下 matWorldInv 的正确性

#4

image
image
如图所示，经过验证通过CCGetWorldMatrixFull拿到的是同一个矩阵，吧localToWorld右乘就对了。
image
还是说IT并不是逆矩阵的意思？我对提示理解有误？

#5

IT是逆转置矩阵一般用来求世界法线和计算光照，cc的shader中没有世界矩阵的逆矩阵，需要自己算

#6

好的，感谢解惑

#7

mat4 inverse_mat4(mat4 m)

{

float Coef00 = m[2][2] * m[3][3] - m[3][2] * m[2][3];

float Coef02 = m[1][2] * m[3][3] - m[3][2] * m[1][3];

float Coef03 = m[1][2] * m[2][3] - m[2][2] * m[1][3];



float Coef04 = m[2][1] * m[3][3] - m[3][1] * m[2][3];

float Coef06 = m[1][1] * m[3][3] - m[3][1] * m[1][3];

float Coef07 = m[1][1] * m[2][3] - m[2][1] * m[1][3];



float Coef08 = m[2][1] * m[3][2] - m[3][1] * m[2][2];

float Coef10 = m[1][1] * m[3][2] - m[3][1] * m[1][2];

float Coef11 = m[1][1] * m[2][2] - m[2][1] * m[1][2];



float Coef12 = m[2][0] * m[3][3] - m[3][0] * m[2][3];

float Coef14 = m[1][0] * m[3][3] - m[3][0] * m[1][3];

float Coef15 = m[1][0] * m[2][3] - m[2][0] * m[1][3];



float Coef16 = m[2][0] * m[3][2] - m[3][0] * m[2][2];

float Coef18 = m[1][0] * m[3][2] - m[3][0] * m[1][2];

float Coef19 = m[1][0] * m[2][2] - m[2][0] * m[1][2];



float Coef20 = m[2][0] * m[3][1] - m[3][0] * m[2][1];

float Coef22 = m[1][0] * m[3][1] - m[3][0] * m[1][1];

float Coef23 = m[1][0] * m[2][1] - m[2][0] * m[1][1];



const vec4 SignA = vec4( 1.0, -1.0,  1.0, -1.0);

const vec4 SignB = vec4(-1.0,  1.0, -1.0,  1.0);



vec4 Fac0 = vec4(Coef00, Coef00, Coef02, Coef03);

vec4 Fac1 = vec4(Coef04, Coef04, Coef06, Coef07);

vec4 Fac2 = vec4(Coef08, Coef08, Coef10, Coef11);

vec4 Fac3 = vec4(Coef12, Coef12, Coef14, Coef15);

vec4 Fac4 = vec4(Coef16, Coef16, Coef18, Coef19);

vec4 Fac5 = vec4(Coef20, Coef20, Coef22, Coef23);



vec4 Vec0 = vec4(m[1][0], m[0][0], m[0][0], m[0][0]);

vec4 Vec1 = vec4(m[1][1], m[0][1], m[0][1], m[0][1]);

vec4 Vec2 = vec4(m[1][2], m[0][2], m[0][2], m[0][2]);

vec4 Vec3 = vec4(m[1][3], m[0][3], m[0][3], m[0][3]);



vec4 Inv0 = SignA * (Vec1 * Fac0 - Vec2 * Fac1 + Vec3 * Fac2);

vec4 Inv1 = SignB * (Vec0 * Fac0 - Vec2 * Fac3 + Vec3 * Fac4);

vec4 Inv2 = SignA * (Vec0 * Fac1 - Vec1 * Fac3 + Vec3 * Fac5);

vec4 Inv3 = SignB * (Vec0 * Fac2 - Vec1 * Fac4 + Vec2 * Fac5);



mat4 Inverse = mat4(Inv0, Inv1, Inv2, Inv3);



vec4 Row0 = vec4(Inverse[0][0], Inverse[1][0], Inverse[2][0], Inverse[3][0]);



float Determinant = dot(m[0], Row0);



Inverse /= Determinant;



return Inverse;

} 我也是从论坛的某个大佬那里拷贝来的矩阵求逆

1赞
#8

用的是逆矩阵的转置矩阵，行列已经转置，右乘
1716791640657

shader
1716791853768

1716792054366

1赞
#9

好帅，我想学这个！