Here's looking at you Tomek, although anyone who knows give me a shout out.
I'm using a nested For...Next loop to render a 2D grid of quads. I need
the grid of quads to be rotated about its "center", but would like to
make a single matrix transformation instead of doing one for each quad.
Is this possible, and if so, how? Even if I have to do multiple matrix
transformations, that is fine, as long as I don't have to do one for
every single quad.
Right now my code (removing all experiments, just bare code) looks like
this:
Public Sub Tile_Grid()
' Draw tile grid texture array in render window.
' General declarations.
Dim TileGridX As Short ' Tile in tile grid texture array being rendered.
Dim TileGridY As Short ' Tile in tile grid texture array being rendered.
Dim TileGridX1 As Short ' Starting tile in tile grid texture array to
be rendered.
Dim TileGridY1 As Short ' Starting tile in tile grid texture array to
be rendered.
Dim TileGridX2 As Short ' Ending tile in tile grid texture array to
be rendered.
Dim TileGridY2 As Short ' Ending tile in tile grid texture array to
be rendered.
Dim PixelX As Short ' Pixel coordinates of tile being rendered.
Dim PixelY As Short ' Pixel coordinates of tile being rendered.
Dim OffsetX As Short ' Number of pixels to offset matrix to
accommodate camera position and tile grid resolution.
Dim OffsetY As Short ' Number of pixels to offset matrix to
accommodate camera position and tile grid resolution.
Dim StepX As Short ' Direction to step through tile grid texture
array loop.
Dim StepY As Short ' Direction to step through tile grid texture
array loop.
' Assign initial values to variables.
TileGridX1 = TileGrid.CenterX
TileGridY1 = TileGrid.CenterY
TileGridX2 = TileGrid.CenterX + TileGrid.Size - 1
TileGridY2 = TileGrid.CenterY + TileGrid.Size - 1
If TileGridX1 < TileGridX2 Then
StepX = 1
Else
StepX = -1
Endif
If TileGridY1 < TileGridY2 Then
StepY = 1
Else
StepY = -1
Endif
' Rotate and translate matrix.
Gl.LoadIdentity()
Gl.Translatef(- OffsetX, - OffsetY, 0)
Gl.Rotatef(- Client.Orientation, 0, 0, 1)
Gl.Translatef(OffsetX, OffsetY, 0)
' Render specified tiles in cell grid to tile grid.
For TileGridY = TileGridY1 To TileGridY2 Step StepY
For TileGridX = TileGridX1 To TileGridX2 Step StepX
' Select texture using its ID.
Gl.BindTexture(Gl.GL_TEXTURE_2D, tTileGrid[Convert.Wrap_Short(0,
TileGrid.Size - 1, TileGridX), Convert.Wrap_Short(0, TileGrid.Size - 1,
TileGridY)][0])
' Create the quad the texture is drawn on.
Gl.Begin(Gl.GL_QUADS)
' Bottom-left vertex.
Gl.TexCoord2i(0, 0)
Gl.Vertex3i(PixelX + OffsetX, PixelY + OffsetY, 0)
' Bottom-right vertex.
Gl.TexCoord2i(1, 0)
Gl.Vertex3i(PixelX + OffsetX + 128, PixelY + OffsetY, 0)
' Top-right vertex.
Gl.TexCoord2i(1, 1)
Gl.Vertex3i(PixelX + OffsetX + 128, PixelY + OffsetY + 128, 0)
' Top-left vertex.
Gl.TexCoord2i(0, 1)
Gl.Vertex3i(PixelX + OffsetX, PixelY + OffsetY + 128, 0)
Gl.End()
' Adjust pixel position.
PixelX = PixelX + 128
If PixelX = TileGrid.Size * 128 Then PixelX = 0
Next
' Adjust pixel positions.
PixelX = 0
PixelY = PixelY + 128
If PixelY = TileGrid.Size * 128 Then PixelY = 0
Next
' Reset matrices so subsequent SDL writes won't get botched.
Gl.LoadIdentity()
End
Notice I didn't assign values to OffsetX or OffsetY. Didn't want to
include any failed experiments. I also attached the code for better
legibility.
I can offset the position of the quads easily using Gl.Translatef, but
the group ALWAYS seems to rotate with the upper-left corner as the
origin. I need to be able to control the origin. I can do this easily
with a single quad, but seem to have trouble doing it "globally" with
the For...Next loops of quads.
--
Kevin Fishburne
Eight Virtues
www:http://sales.eightvirtues.com
e-mail:sa...@eightvirtues.com
phone: (770) 853-6271
Public Sub Tile_Grid()
' Draw tile grid texture array in render window.
' General declarations.
Dim TileGridX As Short ' Tile in tile grid texture array being rendered.
Dim TileGridY As Short ' Tile in tile grid texture array being rendered.
Dim TileGridX1 As Short ' Starting tile in tile grid texture array to be
rendered.
Dim TileGridY1 As Short ' Starting tile in tile grid texture array to be
rendered.
Dim TileGridX2 As Short ' Ending tile in tile grid texture array to be
rendered.
Dim TileGridY2 As Short ' Ending tile in tile grid texture array to be
rendered.
Dim PixelX As Short ' Pixel coordinates of tile being rendered.
Dim PixelY As Short ' Pixel coordinates of tile being rendered.
Dim OffsetX As Short ' Number of pixels to offset matrix to accommodate
camera position and tile grid resolution.
Dim OffsetY As Short ' Number of pixels to offset matrix to accommodate
camera position and tile grid resolution.
Dim StepX As Short ' Direction to step through tile grid texture array
loop.
Dim StepY As Short ' Direction to step through tile grid texture array
loop.
' Assign initial values to variables.
TileGridX1 = TileGrid.CenterX
TileGridY1 = TileGrid.CenterY
TileGridX2 = TileGrid.CenterX + TileGrid.Size - 1
TileGridY2 = TileGrid.CenterY + TileGrid.Size - 1
If TileGridX1 < TileGridX2 Then
StepX = 1
Else
StepX = -1
Endif
If TileGridY1 < TileGridY2 Then
StepY = 1
Else
StepY = -1
Endif
' Rotate and translate matrix.
Gl.LoadIdentity()
Gl.Translatef(- OffsetX, - OffsetY, 0)
Gl.Rotatef(- Client.Orientation, 0, 0, 1)
Gl.Translatef(OffsetX, OffsetY, 0)
' Render specified tiles in cell grid to tile grid.
For TileGridY = TileGridY1 To TileGridY2 Step StepY
For TileGridX = TileGridX1 To TileGridX2 Step StepX
' Select texture using its ID.
Gl.BindTexture(Gl.GL_TEXTURE_2D, tTileGrid[Convert.Wrap_Short(0,
TileGrid.Size - 1, TileGridX), Convert.Wrap_Short(0, TileGrid.Size - 1,
TileGridY)][0])
' Create the quad the texture is drawn on.
Gl.Begin(Gl.GL_QUADS)
' Bottom-left vertex.
Gl.TexCoord2i(0, 0)
Gl.Vertex3i(PixelX + OffsetX, PixelY + OffsetY, 0)
' Bottom-right vertex.
Gl.TexCoord2i(1, 0)
Gl.Vertex3i(PixelX + OffsetX + 128, PixelY + OffsetY, 0)
' Top-right vertex.
Gl.TexCoord2i(1, 1)
Gl.Vertex3i(PixelX + OffsetX + 128, PixelY + OffsetY + 128, 0)
' Top-left vertex.
Gl.TexCoord2i(0, 1)
Gl.Vertex3i(PixelX + OffsetX, PixelY + OffsetY + 128, 0)
Gl.End()
' Adjust pixel position.
PixelX = PixelX + 128
If PixelX = TileGrid.Size * 128 Then PixelX = 0
Next
' Adjust pixel positions.
PixelX = 0
PixelY = PixelY + 128
If PixelY = TileGrid.Size * 128 Then PixelY = 0
Next
' Reset matrices so subsequent SDL writes won't get botched.
Gl.LoadIdentity()
End
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