我尝试使用 LibGDX 实现法线贴图。因此，当我在顶点着色器中计算漫反射和镜面反射颜色时，我得到了一些积极的结果（至少我这么认为）。
顶点着色器：
attribute vec4 a_position;
attribute vec2 a_texCoord0;
attribute vec3 a_normal;
varying vec2 v_texCoord;
varying float v_diffuse;
varying vec3 v_specular;
varying vec3 v_lightVec;
uniform mat4 u_worldTrans;
uniform mat4 u_projTrans;
uniform mat4 u_matViewInverseTranspose;
uniform mat4 u_matModelView;
const vec3 lightVector = vec3(0.0,0.0,-1.0);
void main()
{
// Output the unmodified vertex position.
gl_Position = u_projTrans * u_worldTrans * a_position;
mat3 normalMatrix = mat3(u_matViewInverseTranspose);
// compute the transformed normal
vec3 n = normalize(normalMatrix * a_normal);
// compute the light vector pointing toward the sun, in model coordinates
// x,y compose the longitude and z the (seasonal) lattitude of the nadir point.
//vec3 lightVec = normalize(vec3(u_matViewInverseTranspose * vec4(u_lightVec, 1.0)));
vec3 lightVec = normalize(normalMatrix * lightVector);
// Calculate a diffuse light intensity
//v_diffuse = dot(lightVec, n);
v_diffuse = clamp(dot(n, lightVec), 0.0, 1.0);
vec4 ecPosition = u_matModelView * a_position;
// compute the reflection vector
vec3 reflectVec = reflect(-lightVec, n);
// compute a unit vector in direction of viewing position
vec3 viewVec = normalize(vec3(-ecPosition));
// Calculate specular light intensity, scale down and apply a tint.
float specIntensity = pow(max(dot(reflectVec, viewVec), 0.0), 8.0);
v_specular = specIntensity *
//gloss color
vec3(1.,.7,.3) *
//gloss intensity
.7;
v_texCoord.y = 1.-a_texCoord0.y;
v_texCoord.x = a_texCoord0.x;
vec3 lightDir = normalize(lightVector - u_matModelView * a_position);
vec3 tangent=a_tangent;
vec3 t = normalize(normalMatrix * tangent);
vec3 b = cross (n, t);
vec3 v;
v.x = dot (lightDir, t);
v.y = dot (lightDir, b);
v.z = dot (lightDir, n);
v_lightVec = normalize (v);
}
片段着色器：
precision mediump float;
varying vec2 v_texCoord;
varying float v_diffuse;
varying vec3 v_specular;
varying vec3 v_lightVec;
uniform sampler2D u_texture;
uniform sampler2D u_normalMap;
void main()
{
vec3 ground = texture2D(u_texture, v_texCoord).rgb;
vec3 normal = normalize(2.0 * texture2D (u_normalMap, v_texCoord).rgb - 1.0);
float lamberFactor = max (dot (normal, v_lightVec), 0.0);
vec3 color = ( ground.rgb * v_diffuse * lamberFactor + v_specular);
gl_FragColor = vec4 (color, 1.0);
}
Result:
正如您所看到的，结果已正确呈现。镜面光斑的行为与许多示例类似。但我需要在片段着色器中实现镜面反射颜色以获得更令人印象深刻的图片。所以我找到了例子here http://www.ozone3d.net/tutorials/bump_mapping.php现在我正在努力让它发挥作用。
顶点着色器：
attribute vec4 a_position;
attribute vec2 a_texCoord0;
attribute vec3 a_normal;
attribute vec3 a_tangent;
varying vec2 v_texCoord;
varying vec3 v_lightVec;
varying vec3 v_eyeVec; //Added
uniform mat4 u_worldTrans;
uniform mat4 u_projTrans;
uniform mat4 u_matViewInverseTranspose;
uniform mat4 u_matModelView;
const vec3 lightVector = vec3(0.0,0.0,-1.0);
void main()
{
// Output the unmodified vertex position.
gl_Position = u_projTrans * u_worldTrans * a_position;
mat3 normalMatrix = mat3(u_matViewInverseTranspose);
// compute the transformed normal
vec3 n = normalize(normalMatrix * a_normal);
v_texCoord.y = 1.-a_texCoord0.y;
v_texCoord.x = a_texCoord0.x;
vec3 lightDir = normalize(lightVector - u_matModelView * a_position);
vec3 tangent=a_tangent;
vec3 t = normalize(normalMatrix * tangent);
vec3 b = cross (n, t);
vec3 v;
v.x = dot (lightDir, t);
v.y = dot (lightDir, b);
v.z = dot (lightDir, n);
v_lightVec = normalize (v);
//Added
vec3 ecPosition = u_matModelView * a_position;
vec3 tmp = vec3(-ecPosition);
v_eyeVec.x = dot(tmp, t);
v_eyeVec.y = dot(tmp, b);
v_eyeVec.z = dot(tmp, n);
v_eyeVec = normalize (v_eyeVec);
}
片段着色器：
precision mediump float;
varying vec2 v_texCoord;
varying vec3 v_lightVec;
varying vec3 v_eyeVec;
uniform sampler2D u_texture;
uniform sampler2D u_normalMap;
void main()
{
vec3 ground = texture2D(u_texture, v_texCoord).rgb;
vec3 normal = normalize(2.0 * texture2D (u_normalMap, v_texCoord).rgb - 1.0);
//Added
float distSqr = dot(v_lightVec, v_lightVec);
float att = clamp(1.0 - .25 * sqrt(distSqr), 0.0, 1.0);
vec3 lVec = v_lightVec * inversesqrt(distSqr);
vec3 vVec = normalize(v_eyeVec);
vec3 bump = normalize( texture2D(u_normalMap, v_texCoord).xyz * 2.0 - 1.0);
float diffuse = max( dot(lVec, bump), 0.0 );
vec3 specular = pow(clamp(dot(reflect(-lVec, bump), v_eyeVec), 0.0, 1.0), 8.0 ) *
//gloss color
vec3(1.,.7,.3) *
//gloss intensity
.7;
vec3 color = ( ground.rgb * diffuse + specular) * att;
gl_FragColor = vec4 (color, 1.0);
}
Result:
镜面反射点错误。我认为这是由于错误的矩阵计算而发生的。如果这是真的，为什么前几个着色器可以正常工作？
如何得到model-view矩阵，normalLibGDX 中的矩阵和其他？
viewInvTraMatrix.set(camera.view);
viewInvTraMatrix.mul(renderable.worldTransform);
//model-view matrix
program.setUniformMatrix("u_matModelView", viewInvTraMatrix);
viewInvTraMatrix.inv(); //inverse
viewInvTraMatrix.tra(); //transpose
//normal matrix
program.setUniformMatrix("u_matViewInverseTranspose", viewInvTraMatrix);
//other matrix
program.setUniformMatrix("u_worldTrans", renderable.worldTransform);
program.setUniformMatrix("u_projTrans", camera.combined);
所以，我的问题是最后几个着色器出了什么问题？
问题出在我的模型（网格）中。经过一段时间的挖掘，我发现我的网格没有tangents and binormals。发生这种情况是因为我使用了Blender 2.58无法将模型导出到FBX与切空间。幸运的是，他们修复了这个错误Blender 2.71然后。所以，当你导出模型时，你应该勾选Tangent Space参数并选择版本FBX 7.4 binary。为了确保您的网格包含切线和副法线，您可以使用工具来转换你的fbx文件至g3dj格式而不是默认格式g3db通过使用如下所示的附加选项：
fbx-converter.exe -o g3dj yourModel.fbx yourConvertedModel.g3dj
然后在某个程序中打开它，例如Notepad并检查属性是否包含TANGENT and BINORMAL
"version": [ 0, 1],
"id": "",
"meshes": [
{
"attributes": ["POSITION", "NORMAL", "TANGENT", "BINORMAL", "TEXCOORD0"],
"vertices": [
0.257400, 58.707802, -0.257400, 0.000000, 1.000000, -0.000000, 0.941742,
只有一件事我不明白，为什么lamberFactor使用错误的切线属性（实际上，没有它）？最有可能的是，漫反射颜色计算错误，但在我的示例（在球体上）中，它看起来相当令人满意。我希望它能帮助别人。
EDIT
顺便说一句，为了获得法线矩阵和模型视图矩阵，我使用以下代码：
myMatrix.set(camera.view);
myMatrix.mul(renderable.worldTransform);
program.setUniformMatrix(u_matModelView, myMatrix); //pass model-view matrix
myMatrix.inv();
myMatrix.tra();
program.setUniformMatrix(u_matNormal, myMatrix); //pass normal matrix