Adjacent Triangles

Blitz3D Forums/Blitz3D Beginners Area/Adjacent Triangles

octothorpe

(Posted 2005) [#1]

The shape below is single-surface. It was constructed by addmesh()ing together four meshes. Note the two black pixels along a junction between two quads. There are actually a lot of parallel quads which are joined together without artifacts in this mesh, but that junction is the only one that causes any artifacts. How can I fix this?

;---------------------------------------------------------------------------------------------------
;= TYPES
;---------------------------------------------------------------------------------------------------
type point
	field x#, y#, z#
end type

type shape
	field rotation_pivot
	field origin_pivot
	field entity
	field shape_info.shape_info
end type

type shape_info
	field r, g, b
	field block.shape_block_info[4-1]
	field collision_map[4*4*4-1]
end type

type shape_block_info
	field block_id
	field x, y, ang
end type

;---------------------------------------------------------------------------------------------------
;= CONSTANTS
;---------------------------------------------------------------------------------------------------
const BLOCK_SIZE#         = 1.0
const BLOCK_BEVEL_WIDTH#  = 0.2
; block enum
const BLOCK_end           = 0
const BLOCK_corner        = 1
const BLOCK_straight      = 2
const BLOCK_three_way     = 3
const BLOCK_filled_corner = 4
const BLOCK_TOTAL         = 5
; shape enum
const SHAPE_I             = 0
const SHAPE_T             = 1
const SHAPE_O             = 2
const SHAPE_L             = 3
const SHAPE_J             = 4
const SHAPE_S             = 5
const SHAPE_Z             = 6
const SHAPE_TOTAL         = 7


;---------------------------------------------------------------------------------------------------
;= GLOBALS
;---------------------------------------------------------------------------------------------------
dim block_blueprint_outsideonly(BLOCK_TOTAL-1)
dim block_blueprint_complete(BLOCK_TOTAL-1)
dim shape_colours(SHAPE_TOTAL-1, 3-1)
dim shape_info.shape_info(SHAPE_TOTAL-1)
global block_texture

; used in Calculate_Normals()
Dim Face_NX#(32768)
Dim Face_NY#(32768)
Dim Face_NZ#(32768)
Dim Vertex_ConnectedTris(32768)
Dim Vertex_TriList(32768, 32)

;---------------------------------------------------------------------------------------------------
;= PROGRAM FLOW
;---------------------------------------------------------------------------------------------------
game_init()
game_main()

;---------------------------------------------------------------------------------------------------
function game_init()
	graphics3d 800, 600, 32, 0
	setbuffer backbuffer()

	init_block_blueprint_outsideonly()
	init_shape_data()

	camera = createcamera()
	positionentity(camera, 0, 0, -6)
	light = createlight()
	rotateentity(light, 45, 45, 0)
	ambientlight(200, 200, 200)

	block_texture = loadtexture("block_texture.jpg", 1) ; 64=spheremap, but that doesn't work well on tris with "flat" normals. flare them?
	scaletexture(block_texture, 3, 3)
end function

;---------------------------------------------------------------------------------------------------
function game_main()
	current_shape.shape = create_shape(SHAPE_T)
	entityalpha(current_shape\entity, .5)
	;entityblend(current_shape\entity, 3)

	mousexspeed() : mouseyspeed()
	while not keyhit(1)
		turnentity(current_shape\rotation_pivot, -mouseyspeed(), mousexspeed(), 0)
		renderworld
		flip
	wend
	end
end function

;---------------------------------------------------------------------------------------------------
;= POINTS
;---------------------------------------------------------------------------------------------------
function point_new.point(x#, y#, z#)
	this.point = new point
	this\x = x : this\y = y : this\z = z
	return this
end function

;---------------------------------------------------------------------------------------------------
;= SHAPES
;---------------------------------------------------------------------------------------------------
function create_shape.shape(id)
	s.shape = new shape
	s\shape_info = shape_info(id)
	s\origin_pivot = createpivot()
	s\rotation_pivot = createpivot(s\origin_pivot)

	s\entity = createmesh(s\rotation_pivot)
	entitycolor(s\entity, s\shape_info\r, s\shape_info\g, s\shape_info\b)
	entityshininess(s\entity, .3)
	;entitytexture(s\entity, block_texture)

	for b = 0 to 4-1
		block_info.shape_block_info = s\shape_info\block[b]
		bp = block_blueprint_outsideonly(block_info\block_id)
		rotatemesh(bp, 0, 0, -block_info\ang)
		positionmesh(bp, -block_info\x, -block_info\y, 0)
		addmesh(bp, s\entity)
		positionmesh(bp, block_info\x, block_info\y, 0)
		rotatemesh(bp, 0, 0, block_info\ang)
	next

	surface_id = getsurface(s\entity, 1)
	for v = 0 to countvertices(surface_id)-1
		x# = vertexx(surface_id, v)
		y# = vertexy(surface_id, v)
		z# = vertexz(surface_id, v)
		vertextexcoords(surface_id, v, x+z/2, y+z/2)
	next

	return s
end function

;---------------------------------------------------------------------------------------------------
function init_shape_data()
	restore shape_data
	for id = 0 to SHAPE_TOTAL-1
		shape_info(id) = new shape_info
		read shape_info(id)\r, shape_info(id)\g, shape_info(id)\b
		for b = 0 to 4-1
			shape_info(id)\block[b] = new shape_block_info
			read shape_info(id)\block[b]\block_id
			read shape_info(id)\block[b]\x
			read shape_info(id)\block[b]\y
			read shape_info(id)\block[b]\ang
		next
		for r = 0 to 3
			for y = 0 to 3
				for x = 0 to 3
					read shape_info(id)\collision_map[r*16 + y*4 + x]
				next
			next
		next
	next
end function

;---------------------------------------------------------------------------------------------------
function init_block_blueprint_outsideonly()
	local xy_lookup#[3]
	xy_lookup[0] = -BLOCK_SIZE / 2
	xy_lookup[1] = -BLOCK_SIZE / 2 + BLOCK_BEVEL_WIDTH
	xy_lookup[2] = BLOCK_SIZE / 2 - BLOCK_BEVEL_WIDTH
	xy_lookup[3] = BLOCK_SIZE / 2

	local z_lookup#[3]
	z_lookup[0] = BLOCK_SIZE / 2
	z_lookup[1] = BLOCK_SIZE / 2 - BLOCK_BEVEL_WIDTH
	z_lookup[2] = -BLOCK_SIZE / 2 + BLOCK_BEVEL_WIDTH
	z_lookup[3] = -BLOCK_SIZE / 2

	restore block_blueprints
	while true
		read id
		if id = -1 then exit
		block_blueprint_outsideonly(id) = createmesh()
		hideentity(block_blueprint_outsideonly(id))
		surface_id = createsurface(block_blueprint_outsideonly(id))
		while true
			while true
				read x#
				if x = -1 then exit
				read y#, z#
				x = xy_lookup[x]
				y = xy_lookup[y]
				z = z_lookup[z]
				point_new(x, y, z)
			wend
			if first point = null then exit ; if no points were created, then we're done with this block_mesh
			draw_polygon_with_all_points(surface_id)
		wend
		Calculate_Normals(block_blueprint_outsideonly(id))

		block_blueprint_complete(id) = copymesh(block_blueprint_outsideonly(id))
		hideentity(block_blueprint_complete(id))
		surface_id = getsurface(block_blueprint_complete(id), 1)
		while true
			while true
				read x#
				if x = -1 then exit
				read y#, z#
				x = xy_lookup[x]
				y = xy_lookup[y]
				z = z_lookup[z]
				point_new(x, y, z)
			wend
			if first point = null then exit ; if no points were created, then we're done with this block_mesh
			draw_polygon_with_all_points(surface_id)
		wend
		Calculate_Normals(block_blueprint_complete(id))

	wend
end function

;---------------------------------------------------------------------------------------------------
function draw_polygon_with_all_points(surface_id)
	point.point = first point
	first_vertex = addvertex(surface_id, point\x, point\y, point\z)
	delete point

	point.point = first point
	previous_vertex = addvertex(surface_id, point\x, point\y, point\z)
	delete point

	while first point <> null
		point = first point
		this_vertex = addvertex(surface_id, point\x, point\y, point\z)
		delete point
		
		addtriangle(surface_id, first_vertex, previous_vertex, this_vertex)
		previous_vertex = this_vertex
	wend
end function

;---------------------------------------------------------------------------------------------------
;= DATA
;---------------------------------------------------------------------------------------------------

;= block_blueprints
.block_blueprints

; a list of vertices for drawing polygons.  triangles will be drawn between the first, previous, and current point.
; the second set of polygons for each block are for "inside" polygons, which will not be visible in unadulterated shapes.

data BLOCK_end
data 1,1,3, 1,3,3, 2,3,3, 2,1,3, -1               ; surface
data 1,3,3, 1,1,3, 0,0,2, 0,3,2, -1               ; bevel
data 1,1,3, 2,1,3, 3,0,2, 0,0,2, -1               ; bevel
data 2,1,3, 2,3,3, 3,3,2, 3,0,2, -1               ; bevel
data 0,0,0, 0,0,2, 3,0,2, 3,0,0, -1               ; south edge
data 3,0,0, 3,0,2, 3,3,2, 3,3,0, -1               ; east edge
data 0,3,0, 0,3,2, 0,0,2, 0,0,0, -1               ; west edge
data 0,0,0, 3,0,0, 3,3,0, 0,3,0, -1               ; bottom
data -1
data 3,3,0, 3,3,2, 2,3,3, 1,3,3, 0,3,2, 0,3,0, -1 ; north edge
data -1

data BLOCK_corner
data 1,1,3, 1,3,3, 2,3,3, 2,2,3, 3,2,3, 3,1,3, -1 ; surface
data 1,3,3, 1,1,3, 0,0,2, 0,3,2, -1               ; bevel
data 1,1,3, 3,1,3, 3,0,2, 0,0,2, -1               ; bevel
data 2,2,3, 2,3,3, 3,3,2, -1                      ; bevel
data 3,2,3, 2,2,3, 3,3,2, -1                      ; bevel
data 0,0,0, 0,0,2, 3,0,2, 3,0,0, -1               ; south edge
data 0,3,0, 0,3,2, 0,0,2, 0,0,0, -1               ; west edge
data 0,0,0, 3,0,0, 3,3,0, 0,3,0, -1               ; bottom
data -1
data 3,0,0, 3,0,2, 3,1,3, 3,2,3, 3,3,2, 3,3,0, -1 ; east edge
data 3,3,0, 3,3,2, 2,3,3, 1,3,3, 0,3,2, 0,3,0, -1 ; north edge
data -1

data BLOCK_straight
data 1,0,3, 1,3,3, 2,3,3, 2,0,3, -1               ; surface
data 1,3,3, 1,0,3, 0,0,2, 0,3,2, -1               ; bevel
data 2,0,3, 2,3,3, 3,3,2, 3,0,2, -1               ; bevel
data 3,0,0, 3,0,2, 3,3,2, 3,3,0, -1               ; east edge
data 0,3,0, 0,3,2, 0,0,2, 0,0,0, -1               ; west edge
data 0,0,0, 3,0,0, 3,3,0, 0,3,0, -1               ; bottom
data -1
data 0,0,0, 0,0,2, 1,0,3, 2,0,3, 3,0,2, 3,0,0, -1 ; south edge
data 3,3,0, 3,3,2, 2,3,3, 1,3,3, 0,3,2, 0,3,0, -1 ; north edge
data -1

data BLOCK_three_way
data 1,0,3, 1,3,3, 2,3,3, 2,0,3, -1               ; surface
data 2,2,3, 3,2,3, 3,1,3, 2,1,3, -1               ; surface
data 1,3,3, 1,0,3, 0,0,2, 0,3,2, -1               ; bevel
data 2,2,3, 2,3,3, 3,3,2, -1                      ; bevel
data 3,2,3, 2,2,3, 3,3,2, -1                      ; bevel
data 2,1,3, 3,1,3, 3,0,2, -1                      ; bevel
data 2,0,3, 2,1,3, 3,0,2, -1                      ; bevel
data 0,3,0, 0,3,2, 0,0,2, 0,0,0, -1               ; west edge
data 0,0,0, 3,0,0, 3,3,0, 0,3,0, -1               ; bottom
data -1
data 0,0,0, 0,0,2, 1,0,3, 2,0,3, 3,0,2, 3,0,0, -1 ; south edge
data 3,0,0, 3,0,2, 3,1,3, 3,2,3, 3,3,2, 3,3,0, -1 ; east edge
data 3,3,0, 3,3,2, 2,3,3, 1,3,3, 0,3,2, 0,3,0, -1 ; north edge
data -1

data BLOCK_filled_corner
data 1,1,3, 1,3,3, 3,3,3, 3,1,3, -1               ; surface
data 1,3,3, 1,1,3, 0,0,2, 0,3,2, -1               ; bevel
data 1,1,3, 3,1,3, 3,0,2, 0,0,2, -1               ; bevel
data 0,0,0, 0,0,2, 3,0,2, 3,0,0, -1               ; south edge
data 0,3,0, 0,3,2, 0,0,2, 0,0,0, -1               ; west edge
data 0,0,0, 3,0,0, 3,3,0, 0,3,0, -1               ; bottom
data -1
data 3,0,0, 3,0,2, 3,1,3, 3,3,3, 3,3,0, -1        ; east edge
data 3,3,0, 3,3,3, 1,3,3, 0,3,2, 0,3,0, -1        ; north edge
data -1

data -1

;---------------------------------------------------------------------------------------------------
;= shape_data
.shape_data

; SHAPE_I
data 0, 0, 127
data BLOCK_end,        0, -2, 180
data BLOCK_straight,   0, -1, 0
data BLOCK_straight,   0,  0, 0
data BLOCK_end,        0,  1, 0

data 0,0,1,0
data 0,0,1,0
data 0,0,1,0
data 0,0,1,0

data 0,0,0,0
data 1,1,1,1
data 0,0,0,0
data 0,0,0,0

data 0,0,1,0
data 0,0,1,0
data 0,0,1,0
data 0,0,1,0

data 0,0,0,0
data 1,1,1,1
data 0,0,0,0
data 0,0,0,0

; SHAPE_T
data 127, 127, 0
data BLOCK_end,        0,  1, 0
data BLOCK_three_way,  0,  0, 90
data BLOCK_end,       -1,  0, -90
data BLOCK_end,        1,  0, 90

data 0,0,1,0
data 0,1,1,1
data 0,0,0,0
data 0,0,0,0

data 0,0,1,0
data 0,0,1,1
data 0,0,1,0
data 0,0,0,0

data 0,0,0,0
data 0,1,1,1
data 0,0,1,0
data 0,0,0,0

data 0,0,1,0
data 0,1,1,0
data 0,0,1,0
data 0,0,0,0

; SHAPE_O
data 127, 127, 127
data BLOCK_filled_corner,  0,  0, 0
data BLOCK_filled_corner, -1,  0, -90
data BLOCK_filled_corner,  0, -1, 90
data BLOCK_filled_corner, -1, -1, 180

data 0,0,0,0
data 0,1,1,0
data 0,1,1,0
data 0,0,0,0

data 0,0,0,0
data 0,1,1,0
data 0,1,1,0
data 0,0,0,0

data 0,0,0,0
data 0,1,1,0
data 0,1,1,0
data 0,0,0,0

data 0,0,0,0
data 0,1,1,0
data 0,1,1,0
data 0,0,0,0

; SHAPE_L
data 127, 0, 127
data BLOCK_end,        0,  1, 0
data BLOCK_straight,   0,  0, 0
data BLOCK_corner,     0, -1, 180
data BLOCK_end,        1, -1, 90

data 0,0,1,0
data 0,0,1,0
data 0,0,1,1
data 0,0,0,0

data 0,0,0,0
data 0,1,1,1
data 0,1,0,0
data 0,0,0,0

data 0,1,1,0
data 0,0,1,0
data 0,0,1,0
data 0,0,0,0

data 0,0,0,1
data 0,1,1,1
data 0,0,0,0
data 0,0,0,0

; SHAPE_J
data 0, 127, 127
data BLOCK_end,        0,  1, 0
data BLOCK_straight,   0,  0, 0
data BLOCK_corner,     0, -1, 90
data BLOCK_end,       -1, -1, -90

data 0,0,1,0
data 0,0,1,0
data 0,1,1,0
data 0,0,0,0

data 0,1,0,0
data 0,1,1,1
data 0,0,0,0
data 0,0,0,0

data 0,0,1,1
data 0,0,1,0
data 0,0,1,0
data 0,0,0,0

data 0,0,0,0
data 0,1,1,1
data 0,0,0,1
data 0,0,0,0

; SHAPE_S
data 127, 0, 0
data BLOCK_end,        0,  1, 0
data BLOCK_corner,     0,  0, 180
data BLOCK_corner,     1,  0, 0
data BLOCK_end,        1, -1, 180

data 0,0,1,0
data 0,0,1,1
data 0,0,0,1
data 0,0,0,0

data 0,0,1,1
data 0,1,1,0
data 0,0,0,0
data 0,0,0,0

data 0,0,1,0
data 0,0,1,1
data 0,0,0,1
data 0,0,0,0

data 0,0,1,1
data 0,1,1,0
data 0,0,0,0
data 0,0,0,0

; SHAPE_Z
data 0, 127, 0
data BLOCK_end,        1,  1, 0
data BLOCK_corner,     1,  0, 90
data BLOCK_corner,     0,  0, -90
data BLOCK_end,        0, -1, 180

data 0,0,0,1
data 0,0,1,1
data 0,0,1,0
data 0,0,0,0

data 0,1,1,0
data 0,0,1,1
data 0,0,0,0
data 0,0,0,0

data 0,0,0,1
data 0,0,1,1
data 0,0,1,0
data 0,0,0,0

data 0,1,1,0
data 0,0,1,1
data 0,0,0,0
data 0,0,0,0


;---------------------------------------------------------------------------------------------------
;= MISC
;---------------------------------------------------------------------------------------------------
Function Calculate_Normals(ThisMesh)
; Author: sswift
; Date: 2004-03-25 09:17:35
	
	; Loop through all surfaces of the mesh.
	Surfaces = CountSurfaces(ThisMesh)
	For LOOP_Surface = 1 To Surfaces

		Surface_Handle = GetSurface(ThisMesh, LOOP_Surface)

		; Reset the number of connected polygons for each vertex.
		For LoopV = 0 To 32767	
			Vertex_ConnectedTris(LoopV) = 0
		Next	
	
		; Loop through all triangles in this surface of the mesh.
		Tris = CountTriangles(Surface_Handle)
		For LOOP_Tris = 0 To Tris-1

			; Get the vertices that make up this triangle.
				Vertex_0 = TriangleVertex(Surface_Handle, LOOP_Tris, 0)
				Vertex_1 = TriangleVertex(Surface_Handle, LOOP_Tris, 1)
				Vertex_2 = TriangleVertex(Surface_Handle, LOOP_Tris, 2)
	
			; Adjust the number of triangles each vertex is connected to and
			; store this triangle in each vertex's list of triangles it is connected to.
				ConnectedTris = Vertex_ConnectedTris(Vertex_0)
				Vertex_TriList(Vertex_0, ConnectedTris) = LOOP_Tris
				Vertex_ConnectedTris(Vertex_0) = ConnectedTris + 1

				ConnectedTris = Vertex_ConnectedTris(Vertex_1)
				Vertex_TriList(Vertex_1, ConnectedTris) = LOOP_Tris
				Vertex_ConnectedTris(Vertex_1) = ConnectedTris + 1

				ConnectedTris = Vertex_ConnectedTris(Vertex_2)
				Vertex_TriList(Vertex_2, ConnectedTris) = LOOP_Tris
				Vertex_ConnectedTris(Vertex_2) = ConnectedTris + 1

			; Calculate the normal for this face.

				; Get the corners of this face:
				Ax# = VertexX#(Surface_Handle, Vertex_0)
				Ay# = VertexY#(Surface_Handle, Vertex_0)
				Az# = VertexZ#(Surface_Handle, Vertex_0)

				Bx# = VertexX#(Surface_Handle, Vertex_1)
				By# = VertexY#(Surface_Handle, Vertex_1)
				Bz# = VertexZ#(Surface_Handle, Vertex_1)

				Cx# = VertexX#(Surface_Handle, Vertex_2)
				Cy# = VertexY#(Surface_Handle, Vertex_2)
				Cz# = VertexZ#(Surface_Handle, Vertex_2)

				; Triangle 1
				; Get the vectors for two edges of the triangle.
				Px# = Ax#-Bx#
				Py# = Ay#-By#
				Pz# = Az#-Bz#

				Qx# = Bx#-Cx#
				Qy# = By#-Cy#
				Qz# = Bz#-Cz#

				; Compute their cross product.
				Nx# = Py#*Qz# - Pz#*Qy#
				Ny# = Pz#*Qx# - Px#*Qz#
				Nz# = Px#*Qy# - Py#*Qx#

				; Store the face normal.
				Face_NX#(LOOP_Tris) = Nx#
				Face_NY#(LOOP_Tris) = Ny#
				Face_NZ#(LOOP_Tris) = Nz#

		Next

		; Now that all the face normals for this surface have been calculated, calculate the vertex normals.
		Vertices = CountVertices(Surface_Handle)
		For LOOP_Vertices = 0 To Vertices-1

			; Reset this normal.
			Nx# = 0
			Ny# = 0
			Nz# = 0

			; Add the normals of all polygons which are connected to this vertex.
			Polys = Vertex_ConnectedTris(LOOP_Vertices)
				
			For LOOP_Polys = 0 To Polys-1

				ThisPoly = Vertex_TriList(LOOP_Vertices, LOOP_Polys)

				Nx# = Nx# + Face_NX#(ThisPoly)
				Ny# = Ny# + Face_NY#(ThisPoly)
				Nz# = Nz# + Face_NZ#(ThisPoly)			
				
			Next	
				
			; Normalize the new vertex normal.
			; (Normalizing is scaling the vertex normal down so that it's length = 1)

				Nl# = Sqr(Nx#^2 + Ny#^2 + Nz#^2)

				; Avoid a divide by zero error if by some freak accident, the vectors add up to 0.
				; If Nl# = 0 Then Nl# = 0.1

				Nx# = Nx# / Nl#
				Ny# = Ny# / Nl#
				Nz# = Nz# / Nl#

			; Set the vertex normal.
			
				VertexNormal Surface_Handle, LOOP_Vertices, Nx#, Ny#, Nz#
				;VertexColor Surface_Handle, LOOP_Vertices, polys*127, polys*127, polys*127
		
		Next

	Next

End Function

octothorpe

(Posted 2005) [#2]

A (much) simpler program to reproduce the problem:

graphics3d 800, 600
camera = createcamera()
positionentity(camera, 0, 0, -3)

const BLOCK_SIZE#         = 1.0
const BLOCK_BEVEL_WIDTH#  = 0.2

; lookup coordinates (x and y are identical)
global x#[3]
global y#[3]
global z#[3]
x[0] = -BLOCK_SIZE / 2
x[1] = -BLOCK_SIZE / 2 + BLOCK_BEVEL_WIDTH
x[2] =  BLOCK_SIZE / 2 - BLOCK_BEVEL_WIDTH
x[3] =  BLOCK_SIZE / 2
y[0] = -BLOCK_SIZE / 2
y[1] = -BLOCK_SIZE / 2 + BLOCK_BEVEL_WIDTH
y[2] =  BLOCK_SIZE / 2 - BLOCK_BEVEL_WIDTH
y[3] =  BLOCK_SIZE / 2
z[0] =  BLOCK_SIZE / 2
z[1] =  BLOCK_SIZE / 2 - BLOCK_BEVEL_WIDTH
z[2] = -BLOCK_SIZE / 2 + BLOCK_BEVEL_WIDTH
z[3] = -BLOCK_SIZE / 2

; create block
block = createmesh()
surface_id = createsurface(block)

vertex_0 = addvertex(surface_id, x[1], y[0], z[3])
vertex_1 = addvertex(surface_id, x[1], y[3], z[3])
vertex_2 = addvertex(surface_id, x[2], y[3], z[3])
addtriangle(surface_id, vertex_0, vertex_1, vertex_2)
vertex_3 = addvertex(surface_id, x[2], y[0], z[3])
addtriangle(surface_id, vertex_0, vertex_2, vertex_3)

vertex_4 = addvertex(surface_id, x[2], y[2], z[3])
vertex_5 = addvertex(surface_id, x[3], y[2], z[3])
vertex_6 = addvertex(surface_id, x[3], y[1], z[3])
addtriangle(surface_id, vertex_4, vertex_5, vertex_6)
vertex_7 = addvertex(surface_id, x[2], y[1], z[3])
addtriangle(surface_id, vertex_4, vertex_6, vertex_7)

; translucency better shows the artifacts
entityalpha(block, .5)
ambientlight(255, 255, 255)

; move it around with the mouse to see artifacts
movemouse(400, 300)
while true
	if keyhit(1) then end
	rotateentity(block, -mousey()+300, mousex()-400, 0)
	renderworld
	flip
wend

sswift

(Posted 2005) [#3]

I think you will find the only way to fix it is to trianglulate the mesh properly.

You should tesselate the mesh like so:

   _
 _|_|_
|\|\|\|
 - - -

With one vertex where each vertical and horizontal line meets. That top square should have a \ in it too, but I can't draw both a horizontal line across the bottom, and a slash.

Anyway, that shows that you should have 8 polygons in the T shape, not 4. The reason you get black dots is simply because of floating point inaccuracies. Sometimes you can get away with it, sometimes not. But pretty much all pro game developers set up the meshes like this to avoid those issues.

Also, the difference between this paralell quad and the others is that the others all share vertices on all edges, whereas these two KIND OF share an edge, but the two edges each use seperate vertices, so they're really not the same edge. That's the source of the problem. The two edges don't pass through precisely the same space. When you have two edged which use the same vertices, they're guaranteed to pass through the same space, but here you aren't sharing vertcies, so floating point inaccuracy causes them to be slightly different.

Ice9	(Posted 2005) [#4]

This may be a quick and dirty method that may produce
the results you want. There are UnWeldMesh and WeldMesh
functions in the code archive.

sswift

(Posted 2005) [#5]

Ice:
If those functions do what I think they do, then those won't help. His problem is not vertices which are placed at the same location in space but not welded, it's edges which are not sharing vertices because the vertices are far away from one another and the edges they form just happen to lie on the same line in space.

octothorpe

(Posted 2005) [#6]

That solved it, thanks sswift!