I have to traslate into the z-axis a bit, otherwise I wouldn't see anything on the screen.
Anyway, I'm doing this step by step as you said to me ;) At first i traslate the quad to the origin and in fact i see it there. Then I rotate of 45 degree around the z-axis and I see it rotated right. At last I traslate it again to the previous position, but the quad goes to a different position from that which I expected. Instead, if i do after the rotation: glTraslete(1.0f, 0f,0f); the quad moves of an unit along x-axis as if also this was rotated of 45 degrees, nord-east direction (in order to intend us) and not east- direction as I expect. I hope you undestrand me now :( Paolo p.s. if you prefer I can post my code On 18 Giu, 18:45, Leigh McRae <leigh.mc...@lonedwarfgames.com> wrote: > I am not exactly sure what you're saying actually. At any rate, I > noticed that you're translating along the z-axis. If you're rotating > around the z-axis you don't need to translate along z. Also it could be > that you're translating the quad offscreen since you haven't mirrored > the z translation. > > Anyway, what are you seeing? Did you change the order? I would do it > step by step. Start with getting the translation to the origin right. > Once that looks right then add the rotation. Finally add the translation > back. > > Leigh > > On 6/18/2010 12:35 PM, Paolo wrote: > > > > > > > Thanks for your answer. > > > my matrix is GL_MODELVIEW. > > I have noticed that once I have traslated and rotated the quad, also > > the aces x,y,z seem to be rotated of 45 degree. If it is right, it's > > normal that when i applied the second traslalte the quad goes in > > another position. > > > is it normal? is there something wrong? > > > On 18 Giu, 18:21, Leigh McRae<leigh.mc...@lonedwarfgames.com> wrote: > > >> OpenGL applies it's transforms in reverse so maybe swap the two > >> translates. Sounds lame but this is the sort of thing you get right > >> once and don't look at again for sometime. Also make sure your matrix > >> mode is GL_MODELVIEW. > > >> Leigh > > >> On 6/18/2010 11:58 AM, Paolo wrote: > > >>> Hi leigh! > >>> I've tried, but it doesn't work... the quad goes in a wrong position : > >>> ( > > >>> My quad has these coordinates > > >>> //vertex bottom left > >>> vertex[0] = 9.5f; > >>> vertex[1] = 10f; > >>> vertex[2] = 0.0f; > >>> //top left > >>> vertex[3] = 9.5f; > >>> vertex[4] = 11.0f; > >>> vertex[5] = 0.0f; > >>> //bottom right > >>> vertex[6] = 10.5f; > >>> vertex[7] = 10f; > >>> vertex[8] = 0.0f; > >>> //top right > >>> vertex[9] = 10.5; > >>> vertex[10] = 11f; > >>> vertex[11] = 0.0f; > > >>> and this is my draw function... > > >>> public void draw(GL10 gl){ > >>> gl.glPushMatrix(); > >>> gl.glTranslatef(-10, -10.5f, 0); //to the origin > > >>> gl.glRotatef(45, 0, 0, -1); //rotate > > >>> gl.glTranslatef(10, 10.5f, -2.0f); //back to previous > >>> position > > >>> // Enabled the vertices buffer for writing and to be used > >>> during > >>> // rendering. > >>> gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); > >>> // Specifies the location and data format of an array of > >>> vertex > >>> // coordinates to use when rendering. > >>> gl.glVertexPointer(3, GL10.GL_FLOAT, 0, markerBuffer); > >>> gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, NUMERO_VERTICI); > >>> // Disable the vertices buffer. > >>> gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); > >>> gl.glPopMatrix(); > > >>> } > > >>> On 18 Giu, 17:31, Leigh McRae<leigh.mc...@lonedwarfgames.com> wrote: > > >>>> Translate the quad to the origin, rotate, translate back. > > >>>> Leigh > > >>>> On 6/18/2010 11:12 AM, Paolo wrote: > > >>>>> Hi guys! > >>>>> I'm a newbie in OpenGL. :D > >>>>> I'm trying to rotate a quad around its center. > > >>>>> This is my scenario: I've a quad, drawn with TRIANGLE_STRIP, at > >>>>> specified coordinates. Now I want to rotate of 45 degrees around its > >>>>> center, without move it from its position, not around the origin of > >>>>> the aces. > >>>>> I hope you are able to understand my english... :) > > >>>>> How can I do that? > > >>>>> Thanks > > >>>>> Paolo > > >>>> -- > >>>> Leigh McRaewww.lonedwarfgames.com > > >> -- > >> Leigh McRaewww.lonedwarfgames.com > > -- > Leigh McRaewww.lonedwarfgames.com -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en