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| -rw-r--r-- | Tesselation.txt | 96 |
1 files changed, 95 insertions, 1 deletions
diff --git a/Tesselation.txt b/Tesselation.txt index 61aaf40..6946c8d 100644 --- a/Tesselation.txt +++ b/Tesselation.txt @@ -25,6 +25,100 @@ tessellator/nurbs/quadratics id, only ONE callback-method for one gl-context and "which"-method is supported !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! +Tesselation FAQ: +================= + +Jean-Yves BRUD asked: + +> What is the meaning of parameter signature ? +> If my callback method name is myVertexCallBack (for a GLU_TESS_VERTEX +> callback), +> what is the value of the signature parameter ? + +public void gluTessCallback( int tobj, int which, + Object methodClassInstance, + String methodName, + String signature, + int voidArrayLen1, + int voidArrayLen2, + int voidArrayLen3, + int voidArrayLen4, + int voidArrayLen5 + ); + + +Example (tessdemo.java line 337): + glu.gluTessCallback ( tobj, GLU_TESS_VERTEX, gl, + "glVertex2fv", "([F)V", + 2, 0, 0, 0, 0); + +The signature "([F)V" is the original java style signature of the +argument-list, your callback method takes (here: glVertex2fv) ! + + void glVertex2fv( const GLfloat v[2] ) + + (...) := within the brackets are function arguments signature part + [F := float array + V := void - + the signature part after the brackets + means the return value + +Read SUN's Java Documentation for Java-Callback methods: + http://java.sun.com/docs/books/tutorial/native1.1/implementing/method.html + +Here you can find the mapping of function arguments to its corresponding +string signature representation ! + +Jean-Yves BRUD asked: + +> +> What is the meaning of the 5 parameters: voidArrayLen1, voidArrayLen2, +> voidArrayLen3, +> voidArrayLen4, voidArrayLen5, and what value do I need to put ? +> + +public void gluTessCallback( int tobj, int which, + Object methodClassInstance, + String methodName, + String signature, + int voidArrayLen1, + int voidArrayLen2, + int voidArrayLen3, + int voidArrayLen4, + int voidArrayLen5 + ); + +The maximum number of arrays within the argumentlist of +a GLU Callback function for Tesselation is 5 ! + +So, the arguments voidArrayLen[1-5] refines the expected +size of the arrays, +which are passed into and from the java callback funtion. + + OpenGL-Machine <-> GL4Java-Callback-Handler <-> Java-Callback-Method + +E.g. (tessdemo.java): + glu.gluTessCallback ( tobj, GLU_TESS_COMBINE, this, + "combine_callback", "([D[D[F[F)V", + 2, 0, 0, 2, 0); + + public void combine_callback( double coords[/*3*/], + double vertex_data[/*4xn(=0)*/], + float weight[/*4*/], float[/*m(=2)*/] data ) + { + data[0] = (float) coords[0]; + data[1] = (float) coords[1]; + } + +You can see, we do use the arrays "data" and "coords" with a size of 2 ! +You are not allowed to use nonsense sizes, because this can hurt your +application with a segementation fault ! +(Well the GL4Java Callback functions checks + the array sizes to OpenGL's maximum, .. but be kind of ..) + +The OpenGL machine calls GL4Java's callback function, +which dispatches the call (incl. data) to your java callback function ! + Sven Goethel http://www.jausoft.com -7th March 2000 +8th February 2001 |