Difference entre "glSubDataBuffer" et "glMapBuffer"

Bonjour,

J'utilise les VBO pour afficher mes objets colorés.

Souhaitant mettre à jour les couleurs suivants des variables qui changent à la volé, j'avais commencé à utiliser la methode suivante:

Code:

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            GL.BindBuffer(BufferTarget.ArrayBuffer, VBOid1);
 
            int j = 0;
            for (int i = 0; i < xyz.Length; i += 3)
            {
                if (xyz[i + 2] < 0.3f)
                {
                    if (zdiff[i / 3] > Z)
                    {
                        xyzcolor[j++]= OpenTK.Graphics.Color4.Red.R;
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Transparent.G;
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Transparent.B;
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Transparent.A;
                    }
                    else
                    {
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Transparent.R;
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Green.G;
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Transparent.B;
                        xyzcolor[j++] = OpenTK.Graphics.Color4.Transparent.A;
                    }
 
                    continue;
                }
 
                if (zdiff[i / 3] > Z)
                {
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Red.R;
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Red.G;
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Red.B;
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Red.A;
                }
                else
                {
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Green.R;
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Green.G;
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Green.B;
                    xyzcolor[j++] = OpenTK.Graphics.Color4.Green.A;
                }
            }
 
            GL.BufferSubData(BufferTarget.ArrayBuffer, new IntPtr(countv), countc, xyzcolor);
            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
        }

Qui marchait.
Ensuite, je me suis mis à mettre:

Code:

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            GL.BindBuffer(BufferTarget.ArrayBuffer, VBOid1);
 
            float* ptr = (float*)GL.MapBuffer(BufferTarget.ArrayBuffer, BufferAccess.ReadWrite).ToPointer();
 
            int j = 0;
            for (int i = 0; i < xyz.Length; i += 3)
            {
                if (xyz[i + 2] < 0.3f)
                {
                    if (zdiff[i / 3] > Z)
                    {
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Red.R;
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Transparent.G;
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Transparent.B;
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Transparent.A;
                    }
                    else
                    {
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Transparent.R;
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Green.G;
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Transparent.B;
                        ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Transparent.A;
                    }
 
                    continue;
                }
 
                if (zdiff[i / 3] > Z)
                {
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Red.R;
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Red.G;
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Red.B;
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Red.A;
                }
                else
                {
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Green.R;
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Green.G;
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Green.B;
                    ptr[xyz.Length + j++] = OpenTK.Graphics.Color4.Green.A;
                }
            }
 
            GL.UnmapBuffer(BufferTarget.ArrayBuffer);
            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
        }

Sachant que pour la deuxieme methode, j'appelle Invalidate pour faire un redraw de la scene mais la couleur n'est pas mise à jour..Mais cette methode doit etre mieux coté code.

Merci.

quelle methode il faut utiliser