prepare billboard

src/ShaderGen/CMakeLists.txt

@@ -41,6 +41,8 @@ SET(SHADERGEN_COMMON_FILES  ${STD_MTL_HEADER_PATH}/UBOCommon.h
                             common/MFCommon.h
                             common/MFGetPosition.h
                             common/MFGetNormal.h
+                            common/MFCamera.h
+                            common/MFBillboard.h
 )
 
 SOURCE_GROUP("Common" FILES ${SHADERGEN_COMMON_FILES})

src/ShaderGen/common/MFBillboard.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#include"MFCamera.h"
+#include<hgl/graph/mtl/ShaderBuffer.h>
+
+STD_MTL_NAMESPACE_BEGIN
+namespace func
+{
+    //@link http://www.opengl-tutorial.org/intermediate-tutorials/billboards-particles/billboards/
+
+    constexpr const ShaderBufferSource SBS_Billboard=
+    {
+        "BillboardData",
+        "billboard",
+
+        R"(
+vec2 center;
+vec2 size;
+        )"
+    };
+
+    constexpr const char *GetBillboardPosition=R"(
+vec4 GetBillboardPosition()
+{
+    mat4 cv_mat     =GetCameraViewMatrix();
+
+    vec3 cv_right   =GetViewRight(cv_mat);
+    vec3 cv_up      =GetViewUp(cv_mat);
+
+    vec3 pos        =GetPosition3D();
+
+    vec3(billboard.center,0)+
+    cv_right*pos.x*billboard.size.x+
+    cv_up   *pos.y*billboard.size.y;
+}
+)";
+}//namespace func
+STD_MTL_NAMESPACE_END

src/ShaderGen/common/MFCamera.h

@@ -0,0 +1,31 @@
+#pragma once
+
+#include<hgl/graph/mtl/StdMaterial.h>
+
+STD_MTL_NAMESPACE_BEGIN
+namespace func
+{
+    //@link http://www.opengl-tutorial.org/intermediate-tutorials/billboards-particles/billboards/
+
+constexpr const char *GetCameraViewMatrix=R"(
+mat4 GetCameraViewMatrix()
+{
+    return camera.view*GetLocalToWorld();
+}
+)";
+
+    constexpr const char *GetCameraViewRight=R"(
+vec3 GetViewRight(mat4 cv)
+{
+    return vec3(cv[0][0],cv[1][0],cv[2][0]);
+}
+)";
+
+    constexpr const char *GetCameraViewUp=R"(
+vec3 GetViewUp(mat4 cv)
+{
+    return vec3(cv[0][1],cv[1][1],cv[2][1]);
+}
+)";
+}//namespace func
+STD_MTL_NAMESPACE_END