def _enable_attrib(self, buf_desc: BufferDescription):
buff = buf_desc.buffer
stride = sum(attribsize for _, attribsize, _ in buf_desc.formats)
if buf_desc.instanced:
if self.num_vertices == -1:
raise ShaderException(
"The first vertex attribute cannot be a per instance attribute."
)
else:
self.num_vertices = max(self.num_vertices, buff.size // stride)
# print(f"Number of vertices: {self.num_vertices}")
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, buff.buffer_id)
offset = 0
for (size, attribsize,
gl_type_enum), attrib in zip(buf_desc.formats,
buf_desc.attributes):
loc = gl.glGetAttribLocation(self.program, attrib.encode('utf-8'))
if loc == -1:
raise ShaderException(
f"Attribute {attrib} not found in shader program")
normalized = gl.GL_TRUE if attrib in buf_desc.normalized else gl.GL_FALSE
gl.glVertexAttribPointer(loc, size, gl_type_enum, normalized,
stride, c_void_p(offset))
# print(f"{attrib} of size {size} with stride {stride} and offset {offset}")
if buf_desc.instanced:
gl.glVertexAttribDivisor(loc, 1)
offset += attribsize
gl.glEnableVertexAttribArray(loc)
def _build(self, program: Program, content: Sequence[BufferDescription],
index_buffer):
"""Build a vertex array compatible with the program passed in"""
gl.glGenVertexArrays(1, byref(self.glo))
gl.glBindVertexArray(self.glo)
# Lookup dict for BufferDescription attrib names
# print(content)
descr_attribs = {
attr.name: (descr, attr)
for descr in content for attr in descr.formats
}
# print('->', descr_attribs)
# Build the vao according to the shader's attribute specifications
for i, prog_attr in enumerate(program.attributes):
# print('prog_attr', prog_attr)
# Do we actually have an attribute with this name in buffer descriptions?
if prog_attr.name.startswith("gl_"):
continue
try:
buff_descr, attr_descr = descr_attribs[prog_attr.name]
except KeyError:
raise ValueError((
f"Program needs attribute '{prog_attr.name}', but is not present in buffer description. "
f"Buffer descriptions: {content}"))
# TODO: Sanity check this
# if buff_descr.instanced and i == 0:
# raise ValueError("The first vertex attribute cannot be a per instance attribute.")
# Make sure components described in BufferDescription and in the shader match
if prog_attr.components != attr_descr.components:
raise ValueError((
f"Program attribute '{prog_attr.name}' has {prog_attr.components} components "
f"while the buffer description has {attr_descr.components} components. "
))
# TODO: Compare gltype between buffer descr and program attr
gl.glEnableVertexAttribArray(prog_attr.location)
gl.glBindBuffer(gl.GL_ARRAY_BUFFER, buff_descr.buffer.glo)
# TODO: Detect normalization
normalized = (gl.GL_TRUE if attr_descr.name
in buff_descr.normalized else gl.GL_FALSE)
gl.glVertexAttribPointer(
prog_attr.location, # attrib location
attr_descr.components, # 1, 2, 3 or 4
attr_descr.gl_type, # GL_FLOAT etc
normalized, # normalize
buff_descr.stride,
c_void_p(attr_descr.offset),
)
# print((
# f"gl.glVertexAttribPointer(\n"
# f" {prog_attr.location}, # attrib location\n"
# f" {attr_descr.components}, # 1, 2, 3 or 4\n"
# f" {attr_descr.gl_type}, # GL_FLOAT etc\n"
# f" {normalized}, # normalize\n"
# f" {buff_descr.stride},\n"
# f" c_void_p({attr_descr.offset}),\n"
# ))
# TODO: Sanity check this
if buff_descr.instanced:
gl.glVertexAttribDivisor(prog_attr.location, 1)
if index_buffer is not None:
gl.glBindBuffer(gl.GL_ELEMENT_ARRAY_BUFFER, index_buffer.glo)
def construct_offset_buffer():
gl.glBufferData(gl.GL_ARRAY_BUFFER, 9 * 2 * sizeof(gl.GLfloat), None, gl.GL_DYNAMIC_DRAW)
gl.glEnableVertexAttribArray(1)
gl.glVertexAttribPointer(1, 2, gl.GL_FLOAT, False, 2 * sizeof(gl.GLfloat), 0)
gl.glVertexAttribDivisor(1, 1)