public int SetVertexAttributes(VertexBuffer[] vertexBuffers, int previousAttributesBound, int baseVertexOffset)
        {
            int totalSlotsBound = 0;

            for (int i = 0; i < VBLayoutsBySlot.Length; i++)
            {
                OpenGLESMaterialVertexInput input = VBLayoutsBySlot[i];
                ((OpenGLESVertexBuffer)vertexBuffers[i]).Apply();
                for (int slot = 0; slot < input.Elements.Length; slot++)
                {
                    OpenGLESMaterialVertexInputElement element = input.Elements[slot];
                    int actualSlot = totalSlotsBound + slot;
                    GL.EnableVertexAttribArray(actualSlot);
                    Utilities.CheckLastGLES3Error();
                    int baseVertexOffsetBytes = baseVertexOffset * input.VertexSizeInBytes;
                    GL.VertexAttribPointer(actualSlot, element.ElementCount, element.Type, element.Normalized, input.VertexSizeInBytes, element.Offset + baseVertexOffsetBytes);
                    Utilities.CheckLastGLES3Error();
                    GL.VertexAttribDivisor(actualSlot, element.InstanceStepRate);
                    Utilities.CheckLastGLES3Error();
                }

                totalSlotsBound += input.Elements.Length;
            }

            for (int extraSlot = totalSlotsBound; extraSlot < previousAttributesBound; extraSlot++)
            {
                GL.DisableVertexAttribArray(extraSlot);
                Utilities.CheckLastGLES3Error();
            }

            return(totalSlotsBound);
        }
        public OpenGLESMaterialVertexInput(VertexInputDescription genericInput)
        {
            VertexSizeInBytes = genericInput.VertexSizeInBytes;
            Elements          = new OpenGLESMaterialVertexInputElement[genericInput.Elements.Length];
            int offset = 0;

            for (int i = 0; i < Elements.Length; i++)
            {
                var genericElement = genericInput.Elements[i];
                Elements[i] = new OpenGLESMaterialVertexInputElement(genericElement, offset);
                offset     += genericElement.SizeInBytes;
            }
        }